“Can you or anyone else offer a convincing explanation for why that is the case other than the existence of either an Asian quota or increased anti-Asian biases at Ivy adcoms?”
Yes. The Asian community is more obsessed with Ivy education than any other group. Eg. "The ladder is being pulled away from our feet,” says Tricia Liu. “If we can’t go to the Ivy League universities, how can we get the positions in Wall Street, or Congress, or the Supreme Court?”
And that could well affect the overall quality of the applicant pool as desperate families push/expect their perfectly good but not quite Ivy material children to apply. More applicants from a group does not necessarily mean more admits. I’m not saying this has to be true. But it could be true. There is no way to answer these questions without a lot of very detailed information on the applicant pool which I don’t believe is public. There are a lot of possible explanations for these trends and only one of them is a conspiracy among these institutions to discriminate.