Basically, using academic aptitude as an entrance qualification includes/excludes different races unevenly, (Asians and Whites do better) so this is a way to get round that. Lowering the standards and using randomness is a roundabout way to discriminate against Asians and Whites, but not explicitly. Of course, another way of looking at it is that tests are racist because of the variation in results.
My point is that Universities have a brand for taking top tier raw undergrad students and moulding them into elite graduates who lead the world. In reality, many of those top tier students would succeed no matter what (raw talent, sheer will, family connections, etc).
If you dilute the pool in a meaningful way then 5% of the top 10k students go to Top Tier Uni 1; 5% to Top Tier Uni 2, ... Top Tier Uni 20. In ten years the outcomes of the students will no longer be biased towards Top Tier Uni 1 since students were dispersed across the top 20. Instead they are spread uniformly across the top 20. Why would TTU1 agree to lose their #1 place?
This is predicated on the reasonable belief that the Top 20 Undergraduate programmes are all 'good enough'.
Basically, using academic aptitude as an entrance qualification includes/excludes different races unevenly, (Asians and Whites do better) so this is a way to get round that. Lowering the standards and using randomness is a roundabout way to discriminate against Asians and Whites, but not explicitly. Of course, another way of looking at it is that tests are racist because of the variation in results.