Calling it "gender" instead of "sex" would really fuck up the narrative for these people. A persons sex is scientific standard language. A persons gender is how they feel at that particular moment.
I think this is a great way to start fighting back and changing the narrative.
Yes! Yes! Yes! I can't believe how many seemingly intelligent people have been lulled into using this word. But it's all to a purpose -- make your language imprecise; make your thinking incapable of precision.
Gender - used in grammar as an attribute of a noun. Arbitrary and flexible.
Sex - used in biology as an attribute of an organism. Decided and fixed.
Eh, probably because the left's descent into excessive degeneracy has made the word feel dirty even when used biologically.