Pre-II rejections could signal that they have enough of an applicant pool to fill their class satisfactorily. I think next Friday is go-time, though I'm just guessing based on last year's activity.
If you think about the process here is what happens at most schools.
They start reviewing apps.
Start calling people for interviews as and when reviewers send in an approval.
The reviewers will rank them and based on the rank some may go into rereview/hold file.
They also have a list of people they dont plan to interview for whatever reason along the way.
As the season progresses, they can start interviewing some of the rereview/hold candidates.
They can release the donot plan to interview candidates anytime since a decision has been made.
It is December and they are winding down. They still have 5000 people they have not released or given interviews.
They can start holding 100-200 as standby for remaining interviews and release the rest or start releasing a few at a time. Most schools release everyone at once in Texas at the end of interview season but UTMB seems to have changed it to release a few and it looks like McGovern is testing waters with same.
I would say class filled is not the threshold here since they will be releasing 75-80% or more applicants.
They can only interview 800-1000 at most and receive 6000-8000 apps.