That is, in order to feel it necessary to write something like this, you must be a manager who prioritizes answering the question "what can I do to maximize the happiness and productivity of my direct reports," over "what can I do to ensure my own personal success, regardless of anyone else." Such a person is already going to do the right things, and is much less likely to be hard to work with.
The people who really need these kinds of documents written about them are the ones who are actually difficult to work with - but for many very good reasons, that won't happen.