It actually is really simple. If you’re born with XY chromosomes, you’re a man. If you have XY chromosomes and ambiguous genitalia that can look like a vagina, then you’re a man with a Disorder of Sex Development (DSD).

Men with DSDs will often have elevated testosterone levels because they also have testicles, sometimes underdeveloped and/or undescended. That’s not what makes them a man though, it’s their XY chromosomes.

that’s, like, a third graders understanding of biology and reality is nowhere near that convenient

What is incorrect about it?