I think you are right about that. I've been accepted at a two institutions, and wait-listed at an Ivy, and even for the wait-listed they were very up front about their interest very early (all of them sent "unofficial" notifications even 2 weeks before I got the official notice), while my two rejections both only came in the past week or so. I think the institutions all know when people are getting offers and no school wants someone to accept another offer before they get to even send out offers to prospective students.
Now it's just playing the waiting game to see if the wait-list comes through (but the good kind of waiting).