I'm not sure what brainer is exactly meaning to state. But, yes. Gender, and even almost everything associated with sex, is metaphysics and hence can only be logically coherent, but never proven.

So, it gets interesting when the human mind stumbles onto some forms of worms. Imagine, everyone had a dick and the loser of the wrestliching match becomes pregnant. Or, fish who change /sex/ when it's opportune.

Concepts like "man" and "woman" don't really exist in factual reality. You can try reducing people to reproductive parts. However, that again will say nothing outside the sphere of reproduction. The trouble with metaphysics, unfailingly, is not recognizing just how much we take for granted is make believe. It's both a worthwhile endeavor to study and the most frustrating thing you'll ever encounter.

For example, who can prove genitalia are more meaningful than brain scans? Or, why enforce a policy of "humans can't change sex, so gender is meaningless", when other species very much can? Are only transgender clownfish "valid"?

What happens when we remove pregnancy from the notion of a "female" body by introducing seahorses?

I like to keep my perspectives on pornography and humans separate. Considering trans porn trends most in red US states, that... appears to be the norm. I will not be watching Bg3 sex scenes. For the final result, I imagine this is low importance and may be a bug or unfinished content. Proof of causing problems first, outrage second, you know?