Note how they always enshrine gender in biology, but then make all kinds of non-biological statements about what gender is.

"XX is woman"/"Large gametes is woman"/"can conceive is woman"

And then they'll say

"Women aren't as aggressive", "women are more emotional", "women like being in the home more", "those are women's clothes", etc.

The only reason it's so important for it to be biological is because of how it punishes gender non-conformity and makes the lives of trans people hell. Like it isn't ideologically consistent and they know that. They just don't care. If it was just about genitals or chromosomes, then why is it that gender dictates all these social things about us? The only reason to root gender in how you were born is to ensure gender roles are as rigid and immutable as possible.