My guess is that they offered additional acceptances at the time that final decisions were made last week. (One person on SDN posted that they received an acceptance on Friday.) Last year, final decisions were in mid-March, so the alternate list had moved a bit by this point. When comparing things to past years, I would think that we have to ignore everything prior to mid-April.From threads of the last few years, looks like there have been quite a few alternate acceptances by this point in april. Anyone heard of any so far ?
Personally, I expect acceptances from the waitlist will move slowly until closer to May 15th. Hopefully, the lateness of the final decisions won't adversely affect the waitlist movement too much.