I didn’t know that Michigan was yield-conscious. That explains some really high-stats kids I know who got deferred on early action, made it clear that they really wanted Michigan, then got accepted finally. It also explains kids I know with mediocre academic stats who were applying for the jazz program, who got in. After all, Michigan could be pretty sure that those jazz kids were going to attend, since Michigan was by far the best school they were going to get into, academically, and has a great jazz program. And I could see Michigan not wanting to be the safety school for Ivy aspirants.
I don’t think that they realize that this policy of theirs can backfire. One kid I know of with astronomical stats had this happen to him. Michigan was his first, really only choice, but when he was deferred EA, he also applied to Tufts - which promptly gave him a 25K/yr merit scholarship. He was so hurt by the EA deferral by Michigan that he wound up going to Tufts!