My understanding of biology is derived from actual scientists who, en mass, say that sex differentiation is extremely complex.
What you should be feeling is raw terror that things have got to a state where apparently rational people can put their names to bullshit of that order, and horrifying numbers of people lap it up.
This doesn’t say anything good about where society is at all. Far from it. No surprise that it’s from the US: however bad things are here, at least there are more outposts of sanity and rationality than over there.
To address your point: how complex was it to differentiate the sex of your parents? Is it a mystery which one of them did the impregnating, and which one conceived you, gestated and birthed you (and possibly breastfed you)? Are you saying there’s any actual doubt about any of this, in your case or in the case of every other human being on the planet, who’s ever lived?
Sex refers to reproductive capacity. And it is on the basis of our reproductive capacity, and the relative vulnerability that arises from the fact of being female, that women (female people, who carry the entire burden of reproductive labour) have been oppressed by those of the male sex for thousands of years.
Any attempt to obfuscate that must necessarily be to the disadvantage of the group that has been oppressed, and is still being oppressed, and to the benefit of the group doing the oppressing. Which is why the movement you support and promote is a covert male supremacist movement.
Two sexes, Shizuku. Two. And barring an absolutely tiny number of people with extreme forms of DSD, it is not complex at all to differentiate between them. Which fact the male sex have used to their advantage for millennia. And are still doing now. And you are enabling them. FFS.