Agreed that identifying as homosexual in an environment that strongly encourages heterosexuality takes some of the same skills. Identifying as bisexual is an even closer analog. That is, it's a lot easier for me to notice that I'm not attracted to women and thus different from my heterosexual peers, than it is for me to notice that in addition to being attracted to women I'm also attracted to men; noticing that in addition to wanting a relationship with one person I also want a relationship with a second person is similarly more difficult. (More generally: if X is easier for As to notice than Y is, A1 noticing X says less about A1 (relative to As) than A1 noticing Y does.)

Agreed that this basically raises the floor by some marginal amount.

Agreed that if you can only filter based on one attribute at a time, this isn't the best one to choose if you want to maximize partner rationality. That said, if you can filter based on multiple attributes at once, it might turn out that a filter that takes this attribute into account performs better than one that doesn't, all else being equal.