Hamilton is not forward thinking enough. Not only should his teammate not have access to his data... he shouldn't have access to his own data! He can't talk to the team and the team can't talk to him. The team can just do their best on setup and hope for the best. Lewis can just show up and drive the car. That might fit his personality?!
Seriously it is absolutely ridiculous. It can be "his" data when he buys the team and makes the rules. Otherwise it is the teams's data and not his. Teams should do as they please in this area.
Lastly, he (or anyone) would be a fool to not look at his teammates data. Even if you are already faster. You can maybe learn something you didn't already know.
Richard