ppopp

A composite how exactly? What are you measuring, how are you translating it to a continuous variable, and why are you calling this variable "sex"?

A bimodal distribution of what?

Those are discrete, sex-related developmental conditions, e.g. males with Klinefelter syndrome, females with trisomy X, etc.

People with these conditions aren't middling points on some sort of male-female 'sex spectrum', as there's no continuous variable of sex from which one could obtain a value.

This idea that sex is a spectrum really is nonsensical.

Perhaps it is legitimate to hold that view. I mean, the concept of non-binary requires holding the irrational, non-empirical belief that men and women are loosely defined as a set of sexist stereotypes, rather than sex.

They've taken a socially conservative ideal of what women and men should be like (per whatever culture they're in), assumed that this is what actually defines women and men, and decided to carve themselves an opt-out in the form of an extra category. When they probably should be taking a step back and wondering why they hold these rigid definitions of men and women in the first place, and applying some critical thinking.