Think of the BYU college experience as canoeing in a river. Now, you have some control over where you go in the back and forth across the river, but ultimately, the current beneath you is going to move you downstream whether you want it to or not.

All students come to BYU at different levels in the Church membership spectrum from the nonmember to the most Peter of Priesthood. Each has some control over what is available and happens to them at BYU. They have a canoe and an oar to move freely back and forth across that river. The only spiritual expectation with regards to their enrollment is that they don't turn against the current. The current (or Church) is what makes it possible for the canoe to move down river with far less individual effort than what would be required without that steady current.

The reference point for judging whether a student is going against the current or not is the student's membership status when s/he entered BYU. If s/he was a member (and as a result received even greater financial backing from the Church), that means s/he must maintain her/his good standing in the Church to remain. If s/he was not a member, that means s/he remains a respectful beneficiary of the Church's financial backing of BYU and not denigrate it.

It really is quite simple. Your entry memberships status doesn't really matter. You are only asked to not turn against the current. If you decide that you simply can't continue in life without doing so, then a consequence of that is losing enrollment at BYU. The treatment is equal and fair to both member and nonmember.