Others have said it before, but it could also have something to do with BB just not being fully sure of Brissett as the backup QB, and he wants to get a look at him in camp before he is comfortable moving Jimmy. Perhaps Bill felt that he would rather keep Jimmy around a little while longer just in case Brissett is not up-to-snuff and not be caught with his pants down if he moved Jimmy too soon. If Brissett is deemed to be good enough, Jimmy can still be traded to Cleveland, albeit for probably a little less of a "haul" and for picks next year vs. this year. But, this team is stacked already, so most of those picks would've probably been with next year in mind, anyway.