Would it make much difference? He's not getting in England squads already when he was playing for England every week.
For what it's worth I think there's a very good player in there. Just think him and Koeman are a bad match, personality clashes like this happen in work places.
That's my view too re: Koeman and Barkley.
I think it'd make a difference for any player, seeing a year of their progression wasted. He'd be horribly advised to run his contract down.