This is nonsense that serves only to obfuscate. Normally this sort of stuff is put forward by people trying to confuse and befuddle the reader.

We segregate prisons by sex. Primary and secondary sex characteristics are observable characteristics that indicate one's sex.

Your argument is like saying "You don't buy a Mazda. You go to the Mazda dealership and buy a car that says Mazda on the back, interior, and on the manual. You don't actually know the car is a Mazda."

No, my argument is people mistake a used car lot for a licensed dealership. Just because the salesman says its a Mazda and it has a little logo in the front doesn't tell you much about its history, modifications, etc. Intersex people are in fact pretty common, so much so that there are more intersex olympic athletes than there are trans ones.