I'm not sure that I'm convinced by this model. Truly great work is often a result of consistent professionalism combined with ridiculous productivity.
Consider jashkenas, for example: Over the last few years, he's written an impressive number of solid, professional libraries and released them as open source. So he was working from a high baseline, and he gave himself lots of chances at success. Sooner or later, he was bound to write something 1 or 2 standard deviations better than his personal average.
I'd say that CoffeeScript is at least a 9, but it's an outlier from a pretty large group of 7s.