It's easier to attach your retarded headcanon to a character that doesn't have a lot of backstory or established fandom. When I was looking up stuff about that huge, popular Marauder fanfic (All the young Dudes, of course comes with a "JKR is a transphobe!!! (but I still need to use her characters" disclaimer), it turned out that for some reason since 2020 James and Regulus as a pairing have become a thing and I suspect fujo pooners to be responsible.
Edit: funny tidbit from the
fanlore wiki:
thanks to the already-existing popularity of harry potter combined with the desire to build something separate from jkr combined with, like…the virality of atyd
Lol. Also, the "major bnf (big name fan)" mentioned on that site is referred to as "he", so definitely a pooner.