I've got mixed feelings about that painting too (and would expand on your point).
On one hand it's cool, and it would be cool if he done it on the spot via spontaneous inspiration or even simply planned it out in his head.
But what I would think is more probable, is that he practiced the steps a number of times over and over so that he can produce the desired results in a short amount of time to the point where it's an automated process.. If that was the case it can be said that it's taken the artistic nature out of it.