graduate programs have to report to an accrediting body every few years and report numbers, data and stats to justify their accreditation. One of data points that accrediting bodies look at is the number of students who don't finish their program. Many graduate programs have fewer than ten students per year, so if one leaves, it shows up in the data and the program is held accountable. Having been in charge of this process myself, I can see why a department chair or committee would not want to take a hit with someone who is expected to declare for the NFL after just one season.

Can the administration force a program to take a grad transfer? In my experience, I doubt it.

I'm not saying that BYU should not accept grad transfers, I'm just saying that there are many factors that go into this decision and I would want to have all the information before vilifying the program or administration.