I think it comes from the other direction. Like, the trans and femboy communities are small, but a high portion of them are in tech jobs and FOSS. So this is a stereotype about trans women and femboys all being into Arch, rather than all Arch users being trans women or femboys.
Still overused, but I can see why since the 3 most active communities I see on Lemmy are Linux users, trans people, and Trekkies.