[ianbicking]

"a manager ensures that everyone under him is marching in that direction"

That sounds like a boss to me (and not just because you used an unnecessarily gender-specific word ;). One of the anecdotes in the article is about this person, as a manager, acting as a listening board and ultimately conduit for an engineer when discussing the importance of a specific project at Twitter, and raising questions that came from that engineer that ultimately resulted in the project being cancelled. I think that advocacy role is important management – where the manager advocates both up and down (and ultimately you can't "tell" people what to do, you can only fire them or convince them, so it's "advocacy" both directions).

[nostrademons]

Difference between a "manager" and "boss" is entirely in how they go about getting everyone on the same page. For any given strategic direction, there are a lot of different ways that could be achieved. A good manager takes in information from all her reports (including their preferences, fears, concerns, and goals) and then figures out a plan that keeps all of them happy while also achieving the strategic goals coming down from above. A bad manager takes the goal as the only input and then outputs commands to achieve it.