No, but they are a pre-requisite.  I own and manage a software development company, something you can't easily do if you've never programmed yourself. How do you tell when a very skilled programmer has just run in to trouble from a bad programmer who won't ever get the job done?  Believe me, I've seen "pure" project managers who could not tell the difference.  There's a great deal of subtlety in managing those government projects, and, to my experience, it's rare for a project to be managed successfully without a sound knowledge of the fundamentals.  Of course, you also need much more than just that, and an "ace" coder often doesn't make a good project manager.  But you do need the fundamentals.