If we go meta and generalize the disagreement, the skepticism about "10X" is the same as the rejection of other labels such as "ninja" and "rockstar".[1] For some, the idea of categorizing a subset of programmers with a grandiose label is psychologically distasteful. It doesn't matter what the label is; any label that attempts to stratify programmers is a "myth".
As for "10x" specifically, I'll repeat what I've written before...
To make peace with the "10x" label, I suggest people just think of it as a rhetorical figure-of-speech instead of a rigorous mathematical term. We don't get hung up when people say "Star Wars IV was 10 times better than Phantom Menace" or "I'm not even 1/2 the football player I used to be."
Even if people were to use a new term such as "3-Sigma Programmer"[2] instead of "10X Programmer", the ensuing debates would still be the same.
E.g. "Some people say 3-σ programmers write string parsing loops that are better in speed and quality than 99.7% of the other loops but that 3-standard-deviations-above-the-mean is a myth... etc"
The argument pattern would be the same: take a label, any label, hyperfocus on some literal meaning to the exclusion of all other colloquial usage, and debate why that mathematical interpretation fails in the real world.
tldr: "10x" in discussions is more of an informal ranking of programmer ability and not a rigorous mathematical measurement of output.
[1]https://www.hanselman.com/blog/TheMythOfTheRockstarProgramme...