[Janarealiti]

Well, looking over these two sutta passages, one thing I notice is that neither is really about sexuality per se. The first is about gender roles, and it seems to be mostly about those who are stuck in them (i.e. identify themselves in terms of their masculinity or femininity).

The second is about marriage as a social institution. My guess is that, in the Buddha's time, marriage was defined in terms of heterosexuality and gay marriage simply didn't exist.

It would be nice if a sutta could be found in which the Buddha advised a same-sex couple to be true and respectful to each other and cultivate dhamma together, but unfortuntately none has surfaced, and probably the best one can do is extrapolate from his advice to couples in general.

It's sort of a glass half-empty/half-full situation, I think. Yes, it could be seen as an omission. On the other hand, given that many religions (including some segments of Mahayana Buddhism) make a point of condemning homosexuality, it seems to me significant that the Buddha declined to do so.