It exists, but like, in the same way species exists. The variety and frequency of intersex conditions indicates that it’s two clusters of traits that most species that show this characteristic fall into one or the other of and certain components are remarkably mutable.

That understanding is just fundamentally different from the traditional understanding of two entirely distinct bins that anyone who doesn’t fall into one or the other is a strong outlier and the only alterations are castration or divine intervention (at least in euro-christian tradition).

The two bin model is going to work ok on most humans, it’s not like it’s an obviously wrong one. But as society and science have advanced we’ve found more intersex people that either didn’t know (my cousin would have just been understood as barren, and nobody would’ve noticed my ex’s mom having XY sex chromosomes) or didn’t understand that it wasn’t just some weird quirk that you either hide in shame or just don’t feel is worth mentioning. And anywhere you try to draw a firm line or any trait you try to point to try to ignore the gray is going to leave you with an awkward grouping in some way