To be fair with the commenter you are replying to and as someone who absolutely don’t care about your silly American cultural issues, this use the word gender by sociology is a modern one which redefines its meaning. Historically the word is indeed strictly synonymous with sex.

I still believe that the insistence on erasing previous meanings rather than just using new words is 90% of why the USA is such a cultural cesspit and any kind of discussion turns into a battle but that’s only me.