I think he is talking about how the default is full screen instead of maximize window. Full screen meaning the entire screen with no application and system bar visible and maximized window meaning taking the whole space but still showing the application and system bar. Anecdotally I have seen many more mac users doing stuff in a small window than windows or linux users.
So basically you go from using 30% of solar energy to 33%? Sounds nice but would that really do that much?