It's a bunch of different things. There are layoffs slotted for every month of the year and there is a calendar of all the associated activities. A lot of tomorrow (i.e. today) is RTO related but not all. As far as the waves, different people work on different projects with various critical dates so you will see those who declined to move go off roll at various times.
If you are thinking everyone in a given wave all goes on the same date, no, doesn't work that way. As it shouldn't.
Since there is a bit of a confusion, I’m putting this post from yesterday up, it clears the issue. Source: @cpm+1tpD3MaU