One on ones are hugely valuable, but in my experience managers who emphasize those over team meetings are usually practitioners of differential communication — telling everyone a message customized to make them happy — otherwise known as spin. This is usually associated with new managers who practice a weak form of management, focused on being liked over results. That isn’t this guy’s problem, though!
One on ones should be focused on specific discussions the employee is thinking about. Topics include career development, performance management, company issues, and most importantly concerns they have that need to be addressed before they become truly serious. In that way they serve as an early warning system for issues that are affecting the team.
Think about it, the one on one is probably the only time you are guaranteed to have a direct, personal interaction with your manager that is likely to be more than a brief interaction. It’s definitely the only time you’re not meeting to talk about specific projects. Anything other than mostly listening by a manager during this time is a bad plan.