That's an anecdote, not an evidence. Same as my own revelations after trying to work while being unusually well-rested. The next day the same person may do som

That's an anecdote, not an evidence. Same as my own revelations after trying to work while being unusually well-rested. The next day the same person may do something 10x times faster than you, because of the differences in your past experiences, problem solving methodology, etc. What really matters is amortised performance, and there is no evidence that there exist a significant deviation in such among professionals of comparable experience profiles. Of course, someone who already did something ten times will then do the same or a similar thing in no time, while a completely new problem will be faced with blank eyes by anybody otherwise smart and experienced. It's such an obvious thing that it cannot be a source of a myth on its own.