What defines a BL/GL/QL that makes it not a regular queer romance?
My short answer to that is "I don't have any fucking idea".
My long answer is that personally I go with whatever people decide something is called because it's easier to be understood when you operate within an agreed upon terminology. If the romance is the plot line and other plot aspects take the backseat, there's zero or very little Gay Angst, the themes are reasonably typical of BL since the start and how it has developed, sure, I'll call it BL/GL/QL.
From the manga A Man Who Defies the World of BL
To continue the long answer, I don't view queer romance as a subgenre of romance, but queer is a useful additional label (and an academic term) for not-straight and/or not-cis romance subgenres. Of course, genres are only commonly agreed upon labels, they're not cast in stone, and your mileage may and will vary depending on what you find relevant when categorising works. It's just, as I mentioned above, easier to do as the Romans when in fiction-discussion Rome.
Genre definitions based on themes and form make a fair bit sense to me personally, such as romance, satire and documentary, but genres as a tree structure don't make sense to me at all. A set of labels/tags for various important characteristics of the work in question do make the most sense to me - like "love story, LGBTQIA+, gay/bi/pan male lead character(s), gay/bi/pan male support character(s), South Korea, urban life, paranormal, comedy, animal-human transformation, bar setting" - I'd be interested in a queer love story, side-eye the paranormal bit but be intrigued by the transformation. This is me making a set of tags for a specific show that exists, by the way. It gets classified as a BL, not as a queer romance.
There's already a generally agreed upon characteristc of BL/GL that the most important part of the story is the love story, they're not for instance action shows with a love side plot, which makes the romance/love story label fairly mandatory. Labels indicating that the main love story isn't about heterosexuals would also be ever-present for what we call BL/GL/QL now.
The long answer also includes that romances are not limited to rom-com or lighthearted feelings, but include tragedies, tales of loss, tales of abuse, crime stories and so on and so forth. The number of fiction genres and subgenres is vast - and it makes no sense to me to make a branch on the fiction tree called queer, where pretty much all of the general fiction varieties get a second twig or leaf labelled "queer [insert usual subgenre term]" and then staple another branch to the queer branch and do the same thing all over again with "BL [insert usual subgenre term]". Or stick the BL branch somewhere else in the tree, for that matter.
Side note: a Tumblr post is probably not the best way to revolutionise how the world thinks about genres and labelling of fiction.
Another side note: I'm not dipping into how the terminology is used in Japan, but do read this great blog post by nicks-den. BL history is very interesting and it's always good to know some background. But as Erica Friedman says in the notes to "On defining yuri", "Fan language is free to shift and change with fashion and need, so that it often runs ahead of both commercial and research terminology (...)" - this fan language has shifted a fair bit in the export out of Japan, and the usage a lot of fans globally are familiar with is what I'm talking about.
However the category is defined, the outdated notion that BL/yaoi is more or less steamy gay stuff made for and by straight women shouldn't be a factor in the definition anymore, although some people do like to cling to that idea. There may however be a notable lack of queer community references, because the target audience is generally more widely defined than The Gay People, but as there are cultural differences between such communities, it may just be that as a queer moving in social circle A in region B you miss a reference that's well known in social circle C in region D.
Which means I can't really see how BL/GL differs all that much from any other queer romance, except possibly in that the plot conflicts, the obstacles to the love story, don't primarily have to do with being queer (i.e. the QL lack of Gay Angst). If there's a struggle with acceptance from the couple's surroundings, does that maybe make it a non-BL/GL?
Is SKAM season 3 a queer romance because the main character struggles with accepting his sexuality and with belonging to a community he doesn't feel is relevant, or is it a BL because it's an intense boy/boy romance with very little in the way of sexuality acceptance plot points and very much in the way of other forms of acceptance plot points?
tl;dr I don't like the BL/GL/QL terms all that much.
It's all (queer) romance, as far as I'm concerned. I also happen to be extremely tired of the main obstacle to love and happiness etc. in queer fiction being omg gay. I've practically stopped watching Western queer films because if I have to watch one more teary homophobia scene I may have to maim the director. I want some fucking escape, goddamnit, I want non-heterosexuality to not be a fucking problem all the time in our own fucking media. And this is why I have a permanent grin on my face when watching something where anything can be an obstacle except the queerness. I have actually slowly started to get rid of some of the annoyance with queerness obstacles, some soft BL approaches have been just fine with me, since I said to hell with it and dived into QL.
I don't really have any great suggestions for a better terminology than LGBTQ+ romance/queer romance (I quite like this overview of the genre, although it lacks some common Asian QL traits), but I do have some thoughts.
Perhaps what we in this age and place call BL/GL could be labelled idealised queer romance.
I mean, the usual expectance of a BL/GL is that it's pretty idealised anyway.
(Yes, I'm aware that "idealised romance" is a bit of a pleonasm. A romantic story can be pretty gritty, though. For an example of a romance narrative that's not very idyllic you have literally thousands of so-called regular queer films and books to choose from.)
Seeing as BL/GL often feature a queer semi-permeable bubble where the characters don't have to deal much with being surrounded by straights, and the obstacles to the romance often have little to do with struggles queer people face, the world in a typical QL can be viewed as a fairly rosy picture. In other queer romances, you can bet homophobia is going to rear its ugly head at some point.
Ditching the BL/GL terms would sort out some arguments about for instance I Told Sunset About You - it's romantic, it's Asian (which does tend to make a lot of non-Asian people think BL automatically), but Oh-aew's and Teh's struggles with identity and sexuality practically scream Gay Angst queer romance.
If everything is a variety of queer romance, then I Told Sunset About You is a queer romance, which could also be tagged as idealised by some, while 2gether is without doubt an idealised queer romance.
These two examples are naturally not randomly picked, 2gether is often held up as an example of extremely BL-y BL while there are arguments about which genre I Told Sunset About You belongs to.
(What's more, in Thailand the genres aren't called BL and GL, although they do use those terms as well so that the international crowd understands. It's called waai (วาย) from the letter Y for yaoi/yuri, which is basically as little helpful as BL/GL, but it neatly illustrates a shift in fan language.)
In more recent days and somewhat ambiguous, we have My Stand-In, which dips its toes into the cesspool of homophobia but resolves it BL style easily. Is it an idealised queer romance? Maybe. Do we have to argue at great length about that or can we just call it a queer romance? I think so. Would I call it an IQR (look, groovy acronym!)? I would, but I can see how it could be viewed as not sufficiently idealised.
All in all, I'd like to move on from arguments about whether something is a BL or not, based more or less on personal ideas about what a BL is (I've seen some who seem unaware that non-BL queer shows and films exist) to arguments about how idealised a show is and how central the love story is in it. The volume of arguments wouldn't be reduced in the slightest, but I think it would make more sense as the output of comics/novels/live action shows and films operate now.
Gratuitious My Stand-In gif as a separator before some parentheses finish up the post:
(I've talked a bit about terminology with some friends and I was very insistent to one about having spotted a Greek BL on Gagaoolala, and then I mulled over words and meanings for a while and I also looked in vain for that Greek BL, hence this post. I found two Greek films, but are they BL/GL or not? Gagaoolala has a BL/Yaoi category, but they don't tag films or shows as BL. Is it important how the films are labelled, when I'm able to find what I want to see? (Actually the 'Greece' tag does not work and I need to have words with Gagaoolala, but I digress.) Either way I'm planning on giving both a go. And possibly call them QR or IQR or just bloody IR as I see fit.)
(I may have to revamp this blog to try and make "idealised queer romance" happen instead of talking about BL/GL/QL.)