Seems shortsighted and silly to refuse to allow portal entrants to return to the team. ...
I'm not sure it's an active policy. If you want to roughly group players into categories, we can go with:
1. Players who are really good
2. Players who are fine, but not as good as they think
3. Players who aren't as good as expected
Players in the first group should have no difficulty moving up, and generally find a new home quickly, but they are a minority of the players in the portal. Rourke is an example of group 1. The fact that the offers he got only came from lower tier P5 schools, however, indicates that he is not at the absolute top of group 1.
Players in the third group are players mired in the depth chart, not getting much playing time. They are looking to move down because they want to play, even at a lower level, rather than being a backup. These are the majority of players in the portal. If they don't find a new home, they will be likely out of football. They are very unlikely to return to their old team.
Then there is group 2. They think they are going to move up, but once in the portal, don't find the interest, and have only the options of a lateral move, or perhaps returning to their existing team. If they want to return, with a new sense that they didn't have it so bad, I see no reason why they would automatically be rejected. If they had a terrible attitude to begin with, that was hurting team unity, the team might not want them back, however. I would think it was be a situational thing, not a cut and dried policy.
Since the majority of players in the portal are in group 3, most players who don't find a home will not return to their old team, but I would expect that some players in the second group will end up back on their old team. Personally, I put Bangura in the second group. He's a very good player, but not really a pro prospect, and may or may not be able to find a P5 team that wants him. His best options may end up being a lateral move, or returning to Ohio. We'll just have to wait and see how it develops.