Trans people and allies such as myself don’t argue about the genitals XX and XY produce. However, we recognize that gender is something different than biological sex. For example, what I think of my genitals and who I am because of them is cishet [I believe I was born in a body with the right genitals, and I am romantically attracted to people who are female.]
However, that experience is not universal, however much conviction I might have about my own experience.
I could walk you through how other cultures [Native American, for example] addressed people born with one set of genitalia whose gender was not the same, or how various cultures acknowledge more genders than just two.
Somehow I think you would find it less than compelling, even though it should be: your culture is not the only culture in the world, nor is it necessarily the right one. I don’t know of a scientific way to prove a culture more right or less right, so here:
This might help explain the whole phenotype thing you don’t get. Genotype might result in one thing [genitals], but gender is a phenotype.