PREQUELGATE

Ahaha it's certainly not as deeply detailed as some of my other analysis but the facts are as follows:

John's closest personal friend was Jim Murphy, and his death at Meg's hands is the most devastated we ever see John, outside of his grief for Mary. While it is certainly not explicitly confirmed that they were romantically involved, there is a certain Vibe to it all that is notably different to his reaction to Caleb's death, even though he actually hears Caleb murdered over the phone. It's all very hmmmmmm.

Related to the above, in The Winchesters timeline, John's close personal friend/fellow Marine who was killed in Vietnam is referred to only as Murph— possibly the same Jim Murphy?

Either way, the pendant from Murph's necklace ends up embedded in the skin of John's arm and this saves his life. I am too tired to do a deep analysis of this but the vibes are once again very hmmmmmmm

Again addressing the spnwin timeline, John visibly checks out Carlos. Like. noticeably. And then there is a touch of light flirting and the two share some emotionally intimate moments.

The above bullet points are of course drawing on spnwin and not spn prime and spnwin!John and prime!John are technically two different people from two different universes, but they're universes that are close enough together in terms of timeline that it is not at all unreasonable to extrapolate that the two Johns are probably roughly symmetrical in terms of their sexuality

Also John at one point had sex with THIS WOMAN:

Given the incredible sapphic vibes she radiates, I can only conclude that them banging it out was a case of "I am normally a Kinsey 5.99999999 but your vibes are queer and I dig that so actually I decided gender is a lie right now" attraction on Tara's part. Which, I question her judgment there but there's no accounting for taste I guess.