From looking at previous years as well, it seems that people do remain on WL/HPWL up till the very end. Although there is some movement in May, more movement occurs a lot closer to the start of classes (late June up to July 10). I'm not entirely sure the adcom's definition of "lots of movement" is super clear but rather is more arbitrary than what we might consider a lot (ie. 50% of waitlists or something). Also it feels like who gets pulled off the list is a lot more random and likely driven by meeting other criteria (ie. class diversity/demographics or certain unique qualities of applicants that will make the new class more aligned to what they are looking for).
All this to say, all WL/HPWL people, hang in there, if it's in the cards for this year, then it will be, and if not, then there's always another cycle, and I'm certain we will all become great physicians! This is such a tough journey, everyone should be very proud of how far they've come! <3