But if a team trades for him they have to pay the full prorated $2 million not the minimum. That salary wouldn't have been triggered by the opt-out, he just would have been released.
But sure, he would also have to agree to sign with the team trying to get him, so any number of reasons why he might not, ranging from quality of team to location to how much they would pay him.
It kind of sounds like he was pushing for the call-up, but not so badly that he was wiling to leave, and now they have kind of put him in his place.