I would be interested to see what would happen if they blinded professor interviews to alma mater. Because that might help determine how much of it is bias-- 100%? The inverse correlation would be that people who end up being professors attended those colleges. Maybe they were more likely to get in or are more interested in academia so focused applying to those colleges.
after a true blind interview is done, the result is way more biased than before, so they cancelled that immediately, and replaced it with a process called 'holistic review'.