Why? Colleges are literally places of education. It doesn't seem odd that children who focused on their education would be highly-represented there.
Intervening earlier may make sense - promote education in environments where it's less focused on.
Since Bob came from an environment that did not value education, we might expect to see an improvement from the mere fact that he is now in an environment that does value education. In contrast, since Alice already came from such an environment, we would see no such improvement (from that cause).
I can picture many different things matching this overall impression. Perhaps Alice is the child of two university professors and has vaguely drifted to near-perfect scores without really having to work. Alternately, she has slaved over her books desperate to please her parents and is at the end of her rope.
Similarly, Bob might be a self-educated polymath who has transcended his background, or a crammer who has carefully done everything exactly right to produce the highest score possible, but is almost entirely uneducated outside of the areas that produced good-looking admissions.
I do recall hearing that (at some point in history) the army looked into this and found that black soldiers did better then their white counterparts with an equal score entering. Further, this is presisly the result I would expect to see in the face of generic anti-black bias. For instance, if there was some force that depressed black SAT scores by 10 points and had no other effect, then a black student would be expected to perform as well as a white student who scored 10 points better on the SAT.
The Asians traditionally don't value basketball playing, and why don't the basketball teams try to normalize for students whose childhood environment didn't value basketball playing? Why don't the colleges try to normalize for introverts or working bees whose environment didn't value extroverting or leadership?
You can't possible judge that unless you resort to stereotypes. How do you tell an Asian/Jewish student whose parents didn't put immense value on their education to one that did. You simply can't without making sweeping generalizations based on someone's appearance.
What about the percentage of Jewish students in comparison to their population (US or worldwide)? It kind of debunks that part of the argument when you bring that up. I don't believe this is whataboutism since it should be in the same context and it's already happening.
I don't agree with racial quotas, but there has to be some form of normalization for students whose parents/culture/childhood environment didn't value education.