Hi hello I'm your friendly neighborhood molecular biologist and I want to tell you (or anyone who might think like you) that you're totally fucken wrong lol

It is commonly accepted by contemporary biological scientists that sex exists on a spectrum. The technical definition of sex involves the size of gametes (in humans: sperm and egg cells) that are created by the organism, but we don't usually go around "unsexing" people who don't make gametes (the infertile, the elderly, etc.)

Instead we might look at chromosomes, genitalia, or secondary sex characteristics (beard, breasts, voice, etc.). Although the state of these characteristics often aligns (ie. XY usually means penis and more hair) they for sure definitely do not always.

You can have unusual chromosome combinations (XXY, XXX, etc.), you can have a modification of the signalling pathway for sex hormones (androgen insensitivity), you can have mutations in specific genes relating to secondary sex phenotypes (extra hair, no hair, voice changes, etc.). You might have a person whose gentalia say "female" but chromosomes say "male". You might get a person whose face, voice, and body says "female" but whose genitalia say "male".

You might think these things are too rare to bother with, but intersexuality (defined as a person who's sex can't be conventionally filtered into male or female) is estimated to be as common as 2% of the population (basically the same as red-headed people in the USA). Many people estimate that the actual incidence of unalignment between all sex characteristics as assigned gender is even more common if we expanded the definition to include internal brain structures relating to sexual and gender identity, or natural differences in hormone quantities that overlap between members of different sexes. Basically, science says non-binary is valid as fuck.

That's not even to get into the social construct of gender, but there's a whole scholarly discipline there as well. But I'm a biologist and people weirdly trust essentialist constructs of sex and gender more than social ones, so here I am.