I'm pretty sure I know what you're getting at, but do you mind expounding on your thoughts previous to discovering this information?
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.
I know about the immigration act's effect on the Asian American population because I was an Asian/Asian American Studies major. That your comment received so many upvotes explains some of why these beliefs are so pervasive.
Moreover, our curricula are incredibly tone deaf if this major shift in the American population isn't required knowledge for passing American history.