This one seems to be asking for the reason that I posited.

I can see how it can relate to either "legacy" types of admissions policies, or to the practice that you've postulated, Bostonian, but I think that it probably varies significantly with institution.

This particular institution has a reputation as crushing-- but also has VERY low attrition and high 4y graduation rates, so I'm thinking that they actually are asking on the basis of wanting to know who is most likely to find success at the institution, not necessarily looking for SES/racial balance.

Schrödinger's cat walks into a bar. And doesn't.