sure. and they still can't direct it based on them playing for their school, but rather for the name image and likeness. again, they can put him in their jersey and do whatever they want. Now if he's refusing to do that for them or refusing to complete the things the contract asks for, which can't be based on playing/performance, then yes he's violating the contract.
if this is an early "revenue sharing" thing, then yes that makes complete sense as he would not be entitled to the share from the B10/school. They could also make an argument that he is signing with Miami (or X school) and that this will be a conflict of interest thus violating their contract.
I'm just saying that nothing about his name, image, or likeness has changed regardless of the school he is at which is how those deals are supposed to be reached.
Now what could be really interesting is if they have an appearances clause in their contract that leads to money forfeiture and then they could countersue him and really make this blowup on both sides (given I'd assume that Miami probably isn't going to let him fly up to WI for appearances during game weeks).
In all reality, both sides are at fault. If you were going to shop around, don't take the money. Hard to know what to say about WI in blocking his entering the transfer portal given we don't have all the details, but imagine you could release him and hold him to his contract and sue him down the road for breach if that's really a game he wants to play against a side that has vastly more money and resources rather than blow this into a huge news story