> There will always be deviations from the norm, and given the fact that there are known physical and psychological differences between the sexes[1], I don't see why those differences wouldn't lead to differences in career choice overall.

This sentence is nonsense, which you can tell from how you had to formulate the conclusion. Not "A therefore B" but "A therefore you can't rule out B."

Yes there are gender differences in psychology. But the link between the specific gender differences the Manifesto author pointed to and the conclusion is non existent. The piece is just a bunch of handwaving. It's the Chewbaca defense of sexist ranting.