differences (between the sexes) in engineering aptitude in the general population says nothing about differences in engineering skill among people who have already been hired as engineers

I think Bayes would disagree a little :-) If your prior says blue weasels are generally better at C++ than red weasels, then a red weasel's high test score is more likely to be a random fluke than a blue weasel's equally high score.

ETA: it seems Robin made a similar point a while ago and got crucified for it because he didn't use weasels!