I can see where you're coming from, but the biologism seems very not-human to me. Humans aren't the only species that uses sex for social purposes, but social sex isn't really that common of a trait. Heteronormativity is constructed as if it's biology-centric, but in practice it's so obviously not that it's hard for me to read the Oankali biologism as a similar thing to heteronormativity.

That all the human men in the novel are homophobic about sex with the ooloi strikes me less as "there are no gay men", and more as "emotions are running high, straight men are feeling hugely threatened, and this is a bad time to be out." Plus, maybe, heteronormative selection by the Oankali -- they are the ones deciding who gets to be awake and present, after all. But yeah, that's probably ret-conning on my part as much as anything else, I imagine; just because it can be explained doesn't mean that it wasn't just a plain old oversight on Butler's part.