Why do you base sex on reproductive capabilities, rather than reproductive class? Do you think prepubescent adolescents don’t have a sex?

Good point. I just realized that someone taking drugs for infertility would quickly change between two sexes if they frequently forgot to take it. And yes, I believe that prepubescent adolescents would be in the same category as infertile people.

And do women who’ve gone through menopause lose their sex? If yes, why?

They would be in the same category as infertile people because they wouldn't be able to reproduce which I—remember, I, not everyone else—believe should be what determines sex.

However, this system that I came up with which occasionally beats the current system in providing a definite answer for people with parts of both reproductive systems greatly struggles at differentiating between people who probably wouldn't be able to reproduce in their entire life (people born without a reproductive system or some other crazy thing) and people who just haven't entered puberty yet. This is why I think having scientists check to see what sex a human would be in the future (for kids), and what sexes someone was in the past (for women who already went through menopause).

This doesn't mean that the old system will be useless—even though the article seemed like it was trying to use the excuse that most people aren't biologists to blur the line between male and female, there is still some truth in that statement. Female-only rape shelters would probably be better off if whoever was managing them didn't have to deal with edge cases. In my opinion, it would probably be best if sex-segregated spaces discriminated with the current sex classification system since that's what everyone's used to from socialization and that it's hard to account for less than ~1% of the population unless you're a scientist.