I am a bit surprised if this is new information to anyone who has managed teams and/or thought seriously about the challenges that job has to face. When ever I hear an executive making the assumption that "software engineers" are a fungible resource and they will just move 6 over from the project that is on track and humming along to the group that is behind and in trouble I know they are clueless about managing high performance teams. Every team needs a mix of people and when done well the talents and skills of the individual members complement each other and create an effective whole. Too many people trying to drive, or too many people unwilling to drive as an example can both leave the team floundering and unproductive.

When someone asks me what I think their priority should be as a manager, their day to day job if you will, it is looking for ways to improve this spread of talents to minimize overlap and cover gaps.