(1) Filter requests for work to his team to avoid them having to constantly task-switch, with the associated loss of productivity and job satisfaction.
(2) Provide his team with the business context for the work he asks them to do, and trust them to handle details.
(3) Get his team the support they need to do their jobs.
These all involve tradeoffs. If you constantly tell your team every part of every business discussion that takes place as part of (2), you can fail at (1) and distract them from their long term goals and work.
I've worked with managers that didn't protect their team at all, and who constantly forwarded emails and repeated conversations to us until we could barely get anything done before having to switch to a new task. I've also worked with managers who didn't tell anyone anything, and let their reports toil in the dark for months before letting them know that most of their work was wasted.
A good manager will sometimes fall on either side of the line; a bad manager will consistently err to one side. Managers are just like engineers - there are a lot of bad ones, and some good ones, and size of the company is pretty orthogonal.
