They can still make that decision. Nobody is stopping them from transferring. They're just delaying it for a few months. Honestly, I don't see the problem. Equating it to coaches who can come and go as they please isn't appropriate. Two different situations, IMO.
Actually, they can transfer tomorrow. CU can't stop that. It's a question of a RELEASE.
The RELEASE essentially opens up their recruitment and makes them a free agent. They can be recruited at that point (meaning they can take visits, etc) and they can go on scholarship immediately.
Without said RELEASE, the kids are still free to transfer but must pay their own way for a year. That is obviously prohibitive for most kids, but there is no limitation in terms of transferring to a Juco.
For kids who just played their true freshman years (which is I think close to 100% of the kids considering leaving btw), this can be a good option. If they are that dead set on leaving, they could go to a Juco in January, play in the fall and then have 3 to play 2 as a free agent come this time next year. They would not have missed out on any football (since they have to sit out next fall at a D1 school anyway - so why not play Juco and showcase your talent).
Or they can wait until after spring ball and get a full release and go somewhere. If a school is really interested in them and there is a good fit, they can hold a spot. Spots become available over the summer ALL THE TIME.
Lastly, Colorado is not unique in taking this stance. It is now common to not grant immediate transfers after a coaching change (or "home-sickness" - commonly seen as a temporary condition). Many schools just say no - end of story. If you have a special situation like an ailing parent, that is different.
Our AD has only asked for them to give it a semester. Is it too much to ask to honor one full year at the school that brought you here? NO. It is neither inhumane nor uncommon.