it's possible that part of the lack of transmasc headcanons for female characters comes from a perpetual lack of female characters in media, hence suggesting that a female character may prefer to be male feels blasphemous at worst. the disparity between interest in f/f ships vs m/m ships further makes it feel like poor taste. back in the days where genderbending was more popular in fandoms, i recall some controversy over people genderbending female characters to make yaoi of them with their male love interests. (rarely were there yuri equivalents, if ever) but yeah, at it's core i think it's the lack of dynamic female characters in media causing the gap. it's also worth noting that many trans headcanons are made by trans people themselves, who tend to see themselves in male characters more frequently (once again, possibly because the media they consume doesn't have enough dynamic female characters)
also, if you read homestuck, thoughts on transmasc terezi?
Yeah, I think that’s a pretty good analysis. I try to keep it balanced with transfeminine headcanons of other characters. Part of it is also that a lot of writers write male characters as human beings and female characters as props or narrative devices, so it’s easier to latch onto the men (especially protagonists). And, yes, that there are sometimes so few of them that making them into men just feels tasteless and misogynistic. I think it works better in media with a large or majority female cast for sure.
I’ll admit it has been a whole decade since I finished Homestuck, so my memory is spotty, but a transmasculine Terezi does make a lot of sense to me. I definitely saw myself in her when I was younger. Being a young teen in an emotionally and occasionally physically & sexually abusive relationship with another young teen, having gone through a fair amount of sexual abuse from other kids up to that point, and having a disconnect from my personal & sexual identity that couldn’t be divorced from my gender. I think Homestuck supports a lot of good trans readings in general (transfem Kanaya’s complicated relationship to motherhood comes to mind). That all said I think if you’re doing a transmasc narrative, it’s important not to make the sexism he experiences be the only driving force of his identity, like “escaping womanhood” kind of thing. Then you just end up with Naoto from Persona and that was a mess.