Second, seriously?
A line of code that isn't as clear as it could be in an ipython notebook he probably dashed off in an hour is somehow a reflection on his generosity of spirit? I think you need to recheck your expectations.
A minor correction: the explanation for this heuristic was added later. (I first opened this in a tab, and then didn't read the tab till much later. I also wondered about the heuristic and didn't think to hit reload till I saw your reply.)
But you're right, there is certainly nothing ungenerous from Norvig here. Quite the opposite.