It's funny, when that call came up I didn't even think about the fact that it meant 6O was gay. I just thought it was sort of a given that she'd be interested in a female model, given that from what we can see 9S seems to be the only male android.
The game does a lot of kind of weird things with sex and gender; fitting considering nearly every character is technically a robot of some sort. Eve has a woman's name despite identifying as "male" (though not possessing actual genitalia either way), Pascal identifies as a he despite having a woman's voice, robots have NO identifying sexual characteristics but assume genders anyway via clothing or mannerisms. And the Yorha androids have sexual thoughts and form romantic relationships despite being nearly mono"gendered". Like, does 9S even really know what "Wanting to fuck 2B" actually means? Does Adam? Do either of them even have the capacity? Does it mean the same thing to 6O and her crush? It's a curious thing that it's technically an incredibly sterile world where NOBODY is having actual sex or even has a birth gender and yet sex and gender are still a thing.