Does a Project Manager Need to Have Functional Experience?

I recently had a conversation with someone about the role of a project manager and how knowledgeable a pm needs to be about the functions of the people s/he is managing. The argument was made that a pm doesn’t need to have intimate knowledge of the functions and roles they are managing. I strongly disagreed with this before I heard where that argument stemmed from.

A friend who works at a very large public tech company argued that a pm doesn’t need to have intimate knowledge of the roles of the people they are managing. Disagreeing at first I quickly came around and looked at that statement from another angle. In a large company where processes and expectations of what happens when resources are applied to a project a pm might not need to have functional experience in the roles of people who are working the project.

The breakdown comes when that same sort of thinking is applied to a smaller company or startup where processes are not in place or haven’t been discovered yet. In this case a pm with functional experience in the roles of people working on a project will succeed faster than the pm without appropriate experience. They won’t necessarily have more success but faster and cheaper success.

These are my thoughts…I’m sure there are other or better schools of thought on this.?