I don't think we disagree (?anymore?).

Also in practical informal talk, people overemphasize IQ because it is so fun for hierarchy-minded primates to arrange people from best to worst.

edit re: PCA: Yes, PCA is a super-parametric method, with the usual super-parametric method problems. However, the issue I have with PCA in this context is different, and also occurs in very flexible, fully non-parametric methods. Basically the issue is, no matter how you massage it, the joint distribution simply does not have the causal information you want in it, in general.