If a primary purpose of managers is to "shield subordinates", then you have a much bigger problem within your organization.
As for job security, I guess I'll find out eventually. My gut feeling is that in software companies, it's easier to get laid off/fired as a manager, and it's the opposite in companies where software/IT plays a peripheral or supporting role.
I don't need anyone to tell me to keep working on my TODO list. On the other hand, someone who grasp the big picture is useful to have around to tell me in what order to tackle the task in the TODO list. Its even better when said someone has the clout to go poke a 3rd party that is blocking me so I can keep working on the TODO list.
But the very best managers I have had are the ones that are willing to bite the bullet and say "No, X cannot go into the TODO list as it is now. Let's work together to define what realistic actionable items need to happen for X to be accomplished and then we can put those in the TODO list."
Managers manage. They don't wait until there's a fire and then start running around tossing the blame ball. Boss's do that.
Both of them are distinct from "boss" as the grandparent describes it, which is usually what happens when you get a manager who lacks empathy, awareness, and flexibility. Both leader and manager are highly cognitively-complex, pro-active roles that require constant information-gathering. Boss is what happens when you get someone in that position who lacks the confidence or skillset to stay on top of all that information and then reacts through command & control techniques when things go wrong.
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).
Half of a manager's job is justifying the importance of management to the employees, and the other half is justifying their own importance to their superiors.
Let's put it this way. I have never been kept around long enough to see my own manager get fired. And I have been through 3 mergers.