I think probably physical gender is binary

That's an interesting reply to make with no further details, in response to an article that directly contradicts you.

The outliers are the exception that prove the rule though. The very fact that intersex people exist at all shows that the physical process of inducing the development of sexual characteristics is complicated and messy, and not a simple switch. It's just that evolution has fine-tuned the process enough that in the majority of cases it leads to people who are within ranges that can be considered "wholly male" or "wholly female". So the sexual binary model isn't useless, but it's important to be aware that it is just a model and not reality.

I’m tired, so I’m not looking it up but iirc intersex is WAY more fucking common than you think and there are SO MANY ways it can happen. It’s not very rare outliers, but people also fuckin mutilate their kids over that shit and plenty of stupid shit so here we are thinking it’s like .01% of people.

Rare, sure, but keep in mind that even a 0.2% incidence rate means that 16 million people wouldn't fit the binary gender model. And that's the most conservative estimate for the condition given in the article. 6% puts it closer to half a billion people.