It obviously is in the school’s self-interest to admit much of the class ED:
a. Yield is more predictable. (i.e. less likely to fall short and go to the waitlist, or overenroll)
b. Yield is higher. (i.e. minor rankings and perceived desirability benefit)
c. Skews the applicant and admit pool to higher income applicants who do not need financial aid. (i.e. lower financial aid expense)
Given how popular the school is, it is not surprising that it can get away with “stacking the deck” in its favor.