It’s also not true there are only 2 biological sexes in humans (irregardless of the social arguments that exist in current day discourse)

I mean, it depends on how you define the term "biological sex", which really is a fuzzy term that can refer to distinct things. There's two types of gametes in humans and intersex people and everyone else still has X or Y chromosomes not Z or something. In that sense there are very much two sexes. Phenotypically of course there's tons of variations but unlike with plants an individual carrying both male and female gametes in one body is exceedingly rare, that is, our biology does generally speaking prefer our reproductive phenotypes to be dimorphic whereas the biology of most plants is happy to have individuals carry both types, switch around, and whatnot. It's wild over there. Imagine you're hanging out with the gals and because there's so much gal pheromones floating around your body decides to switch into hairy woodchuck mode and grow a dick. That kind of flexibility is generally not what enbies mean when identifying as enbies.

...because that's just the reproductive aspect. It gets progressively more complicated and less sensible to talk about a binary the further you get away from that, what we get instead is bimodal distributions: Distinct peaks, but also overlap. Sticking to easily measurable things: The height of an individual human (within a single population and social class i.e. let's ignore malnourishment) is not entirely useless as a predictor of that individual's sex. Once you get to general behaviour, let's say "enjoys walks on the beach more than going clubbing" all bets are off.