You have a point. However, a) most forts fail before becoming that populous, b) you could easily get a mismatch with such small numbers (1 gay dude and 1 gay gal, 3 gay dudes, etc.), and c) having 2-4 gay people live together does not necessarily mean that they will pair off. People won't necessarily get along and relationships are more complex than that.
Though, of course, one could code it to ignore compatibility - even though DF already simulates couple compatibility to some degree.
And anyway, why does it matter? So the gay people end up more likely to stay single, not because it's hard-coded that way, but as an emergent thing due to the numbers involved. I think that's fine. In fact, it could make for interesting stories/character development (when that sort of thing is more developed in the game) to have gay people have trouble finding mates. It's not necessarily unrealistic either, especially for, say, small villages, assuming that 1 to 2% number is correct (I personally think it's somewhere between that and the 10% given before, but that's neither here nor there).
But anyway, it's true that there's plenty of threads on the subject, and further discussions on the subject might be better off in there.
It does make me wonder, though... has any indication been given on when romance and such will be implemented in more detail, or how high of a priority Toady considers it to be? Also, what were those few (four, I believe) possible paths of development after the current release again that Toady mentioned recently? I think it was in the devlog, but I can't find it anymore. Does anyone remember?