Previously, my somewhat-nebulous thoughts on this were: there's definitely a math/sci stereotype about Asians; don't read too much into stereotypes; but Asians really are disproportionately represented among the math/sci fields; what on earth would explain it if not a genetic and/or cultural bias? >cognitive dissonance<

As I said, nebulous; I hadn't really pursued the line of thought very far, just tangentially as it came up elsewhere. I hadn't known about the 1965 Act, and its existence and the above analysis just instantly explained so much so well and without reference to Asians somehow being magically different; just that the math/sci trait had been selected for within the Asian-American population.

Not that it rules out other explanations. But it's so blindingly obvious (in retrospect :) that the Act would have some effect along these lines, that Occam's Razor raises the bar for other explanations by a lot.