Actualy, Dr. Kegan covers all the points you raise. Another commenter expressed it well. Nobody is "at" a singe stage. We have, as you and Kegan both rightly note, the potential to act from any of these levels. The point is that during various long (years) periods of our live, there is a general "center of gravity" such that we have tendencies to act more frequently from within a certain perspective. You might want to look up his research. He even developed a specific model for deveopmental research to test his theories.