People with 2+ acceptances can only hold one at a time. so they must drop all other acceptances but one but may stay on any waitlists they choose to do so.
This means waitlist movement can start moving as people drop seats. And if they then get off a waitlist spot and have another seat held somewhere, they again have to choose within 1-2 weeks or in the case of buffalo 24 hours. Then again waitlist movement goes again. It goes back and forth like this the rest of the summer. Most of it will occur now til end of May early June. Starts slowing down in June with it really tricklking around end of June and early July at most schools. Schools that are higher ranked have less movement, but many state schools and lower tiered schools have a lot of movement.