This is an eternally frustrating topic. The 10x effect is very real, not mysterious ... and also somehow very overhyped.

The original research in the 1970s didn't claim some programmers were 10x average, just that some were 10x some others. That is directly observable in any shop with more than a half dozen people.

There are "10x typists" too. I type 65 words a minute, sad as a typist but fast for an engineer. Our admin types something crazy like 170 wpm. People who never have a typing class can be 15-20 wpm. 170/17 = 10x. I'm sure a real typist would say 17 wpm people "can't type." From that person's perspective it's true.