That isn't at all an expected result. Given the range of physical differences between men and women it is quite surprising if there are no mental differences on average and potentially even in extreme situations. Hormonal differences alone could cause any sort of strange divergences and it might have turned out that the ability to pump blood to the brain (ie, raw physical fitness - which is clearly a divergence between the sexes particularly on the tails of the distribution) is a contributor to peak mental processing ability.

It isn't expected that men and women are the same in how they do things. We just don't think the differences are important to what outcomes get achieved when it comes to real-world problems.

EDIT

And something interesting, my understanding is that where men are more likely to be red-green colour blind women go in the opposite direction, sometimes even as far as having tetrachromacy/a 4th type of colour receptor. Maths always seemed to me to be linked to vision, that sort of thing might trigger all sorts of strange results.

Biology is really messy.