Of course, UMich has NOT been reviewing all their applications for the last 5 years, at least? I don’t buy this theory.
But, yes, the multiple releases of deferred/RD and RD decisions (2/1, 3/1, 4/1 and mid-April) is a bit too much. Just have one deadline and announce 1 or 2 decision dates. One in December and then one in March with all the other public schools like the UC’s.