I think it would be more reasonable to call someone a 3 -sigma dev (someone 3 standard deviations above the mean. These would exist because that's how stats work)
The gambit is that a mediocre programmer would take 10x as long to write the same code as the hypothetical 10x dev. But that’s not what a mediocre or even average dev does: they solve the problem in an entirely different (and, for purposes of this argument, less optimal) manner in some spam of time that may or may not be longer than a qualified hacker or a theoretical 10x dev. Almost all CS problems have multiple solutions, so you’re not likely to find one where there is only one solution and it takes one guy x and the other guy 10x as long.
Also, you're not guaranteed to have an example 3 standard deviations above the mean. It strongly depends on your distribution and sample size.
You're right about the sufficient sample size.