No, what you said isn't accurate. There is no such thing as multiple PTEs, there is only multiple As.
@fatherofdragons is correct -- the seat isn't open until the applicant withdraws or the school rescinds,
neither of which HAS to happen on 4/30, despite the risk of the school doing the latter if the student doesn't do the former.
Although anything is possible, LOTS of schools will reach out to accepted students after 4/30 to confirm their intentions before unilaterally rescinding them if they haven't formally withdrawn, and there cannot be WL movement with respect to these potentially vacant seats until this happens, which could be early on 5/1 or days later, depending on the school's policy and sense of urgency.