"10x" is a very specific, concrete statement about programmer productivity. And when people use it, they take it as a literal statement. And they apply it across the board. They think a "10x" programmer can actually write any code 10 times faster than an average programmer. But nobody can even quantify what programmer productivity is, so concrete statements like "10x" are misleading.

Even in this thread. Saying John Cormack is a "10x" programmer because he wrote Doom seems silly. (No offence to John Cormack.) There are lots of games out there. Why Doom? Or is it that anyone who wrote a game is a "10x" programmer. Or Linus Torvalds, why does writing Git make you a better programmer than writing Subversion? And what is "productivity" when writing code for yourself, versus writing code for your employer?

Einstein was not a "10x" scientist. He was a genius. The only problem is that there aren't many Einsteins out there. To make it your goal to only hire the Einsteins of the world, or to try to figure out how to 'make' more Einsteins, is short-sighted for an employer when there so many good, but non-genius programmers out there. But if that is your goal, at least be honest and say you are looking for geniuses.

The term "10x" is a literal measure of productivity. It defines the rate of output per unit of input. And that is why it is a myth.