Bc even in the omega world they still want females and males together I guess? If the world is mostly beta then you get the normal maleXfemale attraction, the usual bio babies and things like that. And somehow a male O should be attracted to a female B or A, and vice versa since everything else is MxF. I'm spitballing here bc otherwise idek.
Omegaverse is an imaginary world. And I like it when authors experiment with it and give something unique. In this case, I think society still prefers hetero couples over homo couples. Like that dude was beaten by his father because of his orientation. We don't usually see the topic of homophobia in Omegaverse. So this one is quite interesting to me.

Its an omegaverse so why is it wrong that they are gays ???