And that's the key. You're positing that the disadvantage magically stops in university.

I work in law school admissions prep, and you see these disadvantages all the way down the line: SAT, college grades, LSAT, law school grades, Bar exam passage rate

There are some cases where it stops. Maybe the college board can identify which variables may indicate a poor correlation. There might be some factors that indicate transient issues and some that indicate worse lifelong expectations.

But I'd be cautious about too readily assuming that a cause of a lower SAT will vanish in later life.