One obvious difference between how the AVSAB and SAT are used is that the minimum score on the AVSAB is ~ 35th percentile (somewhere around a 980 on the SAT). That kind of score is likely all-but disqualifying at Columbia, where the 25th percentile is 1450, and only 5-6% of applicants are accepted.

The question is not “does the SAT provide some globally useful measure of college performance,“ to which the answer is “very probably yes”; instead, Columbia is asking “does requiring it help them identify top tier talent from underrepresented backgrounds rather than filter out top talent from those backgrounds”, to which the answer is “quite possibly not”. They aren’t banning it as a factor, they are just permitting those with a low score to omit it.

And lest I sound like I’m cheerleading elite universities here, I suspect there are enough people with >1500 SATs and family incomes <$50k that you could fill 2 whole Columbias. They’re obviously going to keep admitting legacies and other high donor value applicants because they’re mostly trying to maximize return on investment.