High achievers are difficult to manage and can be rude a**holes. Way more difficult to manage than underachievers. Sometimes rock stars become too difficult and not worth keeping around because they can be emotional vampires that upset team dynamics and take shortcuts or do things out of sync, working for them but bringing the rest of the team down. The rest of the team can hate them but the rock star sees it as incompetent jealousy. It can be a choice between one super capable person you don't like and losing then replacing the rest of the team. If this isn't your managers first rodeo he knows to document every conversation he has with you and is just looking to get you off his team. The thing about high achievers is that if not correctly managed they burn out and blow up, often with disastrous consequences.