I haven't come across that term, yet, and after reading the article, I am even more puzzled, how any sane person could ever come up with such a bs. Sure, there might be researchers releasing one of their awesome statistics. But have you ever read the fine-print?
Statistics always only benchmark a very certain situation. In the text it says that they measured the time needed to solve a set of problems. How well did they solve them? Are the solutions reusable? Decoupled? Easy to use, maintain and upgrade? Are they well documented?
In addition to the actual quality of the source code and documentation, there is no hint about the mental and physical condition those individual programmers where in or how their experience spectrum looked like. Maybe the slowest was tired, hungry, just had a divorce the day before and in general was more of a "jack of all trades", up against more specialized programmers. The statistics won't tell you, they only state that there were a few programmers who were "slow" compared to some other programmers.
Since "10x developer" is such a relative term and based on statistics no one cares to understand correctly, how comes people actually have the confidence to bring up such a term? Imho, "10x developer" is bs and we should abolish that concept.