Also, many who get into this school also get into schools like SUNY Downstate, Upstate, Hostra, Stoney Brook, etc. (I glanced at the profiles of a bunch of people on the WL and who got As and saw this trend) so even if they don’t get into the top tier schools like you mentioned, many still have to choose between some really good schools so that could also be why this school has very good WL movement.
And when it says they take 50 off the WL, does that mean 50 who are taken off the WL and matriculate? Or do you think that includes people who get the A and turn it down?