I wouldn't stay in an RP where the GM did any of that.

I don't think that specifying the gender of the characters necessarily needs to have anything to do with romance or smut. It could be friendship relationship too, or just a preference by the one who started the interest check. It might even be that you see everyone else writing interest checks like that and you end up doing the same. 

I don't know if you'd find someone like that. I'd say it's worth the try though. It can be very difficult to find someone who's serious for a 1x1, but it's also the most rewarding, fun and creative way of RPing in my experience if you do find a good partner.