The term that might help you is “oogenesis”.

Essentially once cells have begun dividing following fertilization some are set apart as germ cells. These are the cells that eventually become gametes. The thing is, like I tried to mention in my last reply to that guy, it isn’t strictly chromosomes that determine what these cells become in humans. Lots of genetic transcription and translation factors, hormones and hormone receptors, ligands and so on. Sometimes those cells don’t even make it into the gonad, they die, and are absorbed by the embryo’s body.

This is why sex isn’t a binary, there is a spectrum of outcomes following gametogenesis, including a lack of gametes. Statistically it is most likely for a person who is born XX to have primary and secondary female sex characteristics. But that doesn’t mean people who fall outside of that aren’t also biologically women. If you define a woman as someone that is born with eggs, you deny womanhood to millions of people that would otherwise be considered a cis-woman by outdated standards.

That person stated one argument and then kept changing it, eventually arguing that we just weren’t understanding his words. Either he’s willfully ignorant and pushing a definition that is not taught in American universities, or he has an agenda. And the refusal to acknowledge the 30+ comments telling him he is wrong really suggests that there is an agenda.