I’m not sure there’s any indication that he “stormed out.” If he’s having surgery and won’t be back at the stadium this season, it would be logical to clear out the locker.
That being said, it seems as though this should have been coordinated in advance with the team and a statement issued. The seeming lack of communication between Ohtani’s agent and the team is what concerns me. But after seeing that guy’s recent press conference, my fears are somewhat eased. The agent is a moron. That was a horrible performance.