Viewing the last 4-5 years for the blue blood programs I noticed that, for example, Alabama signs typically no less than 25 (often more up to 29) guys each year. Simple math indicates they sign typically 100 guys in four years plus the redshirts on year zero. Out of 85 scholarships, they lose about 21.25 each year plus any that go pro. Thus, on any given season (attrition aside) they must have 1-5 guys they must "get out" of the program somehow.
Said all that to ask this:

How does a blue blood program actually get a guy out of the scholarship pool if they need to upgrade?

Can they unilaterally pull a scholarship to a passing student? Assuming they can't, is it legal for donors to underwrite an "orphaned" scholarship player? Or do they just tell the kid "you're not going to play, I suggest you go to the portal."?

Just curious about the everyday mechanics of all this.