This claim relies on us being able to reliably sex skeletons. What is the false positive rate? How accurate are we in archaeology where the skeleton has been underground for a long time?
If you have a pelvis or even a sacral bone recognizing typical male from female is trivial.
How many false positive errors can be made? No idea, but if your bones during several years are bathed in a sex hormones cocktails different from what your sex chromosomes are indicating, then on a body plan level you are not what chromosomes are saying.
It is debatable if such mix up is a classification error.
I was under the impression that they later confirmed his sex as female using the DNA sample