I think whether someone is a 1x or 10x developer can depend a lot on what it is that they're working on. If its a codebase they're intimately familiar with, in an environment where they have a fair amount of experience, they can very easily be a 10x'er. Meanwhile, drop the exact same person into the middle of a large project they have little overall grasp of, and they instantly become a 1x'er.

Sure, there is a level of innate ability. And there are plenty of people who will never seem to progress in productivity no matter how much time you give them. But beyond that, how good of a fit the project is for the person can play a huge part in where they fall on the scale.