Why is BU considered low yield?

Okay, this is a semi-rhetorical question. It's obviously low yield because everyone and their dog wants to live in Boston, and most people don't have a realistic shot at Harvard, so BU (and Tufts) get close to 12,000 applications each. Attractive urban location+relatively low admitted stats=low yield school. But BU's stats aren't actually low at all. The mean accepted student's cGPA (per MSAR) is 3.81, the sGPA is 3.80, and the MCAT is 517. That's just a hair less selective than Einstein,... Why is BU considered low yield?
Source: Student Doctor Network - Category: Universities & Medical Training Authors: Source Type: forums