It's an allegory for any "extremely niche" interest that would have been considered super weird before these people could easily find eachother, although OP probably had furries and people like that in mind.
Yeah, I've mostly heard this mentioned in reference to really obscure fetishes that you'd probably never have a chance to indulge in if it weren't for the internet.
I remember an early wtf Internet moment for me on fark.com someone linked a car-fucking forum complete with diy "muffler cosies", etc. Probably at least half joking, right??