that job description is that it requires knowledge of the work itself. You can’t effectively manage a team if you don’t know the intricacies of what they’re working on. That doesn’t mean every programming manager has to be a programmer (although it helps) nor that every design director has to design every screen (but again, it helps if they’re able to). No, it means they should know what needs to be done, understand why delays might happen, be creative with solutions to sticky problems, divide the work into manageable chunks, and help put the right people on the right projects.
