"And if mathematical ability were distributed as a Gaussian,
and genetic, women couldn't be ascending so rapidly."
This is false. It could be that mathematical ability is genetic and normally distributed, but some component of women's underrepresentation is caused by factors other than this (e.g., discrimination, personal preferences).
"It's just no good at drawing conclusions on the extremes of ability. A better guide might be actual performance. The IOI this year had more girls than ever before -- 11... Were the 'standard deviation' explanation correct they should have, instead, had 0.4 girls earning maybe 0.01 medals."
Come on. I know you know better than to draw statistical conclusions from a single event with a sample size of 11. So why do it?
"The fact that g is non-zero can be readily explained by the following simple observation -- most academic subtests, including IQ's, rely on skills that are either practiced as a group, or on skills that are shared between subtests. One example is focus, in general. Another is visualisation. Another is working memory. And so on and so on."
You've come up with a plausible theory of what g is. It might be f(focus, visualization, working memory). This does not make the theory of psychometrics "totally absent of content", it just means they don't understand everything yet.
The fact that pressure is non-zero can be readily explained by the following simple observation -- air is made of particles obeying Newtonian mechanics which impart a force upon a vessel when they collide with it. Does this make thermodynamics "totally absent of content"?
The fact of the matter is that a variety of seemingly unrelated tests are correlated with each other. They are also strongly correlated with various life outcomes in a manner which more or less corresponds to our intuitive intuition about the idea of "intelligence". Stuff like this rarely happens by chance, and it is highly likely there is something behind it.