I like to think we are all 10x developers. The question of a 1x developer should be how to grow their productivity (assuming they are motivated to do so). Less productive developers should not feel like they have one tenth of the natural talent someone else has. Instead they should look at how they can improve their work flow/knowledge and companies should try and maximise the output of their employees.
Yes some people will always be better/more productive than others, but most people are differentiated by completely controllable factors.
Well, that's why the author had to call tech leads "100x developers". x inflation has led us to this situation where 10x is now a baseline minimum. Anything under 100x is just mediocre.