My biggest problem with 10x is that it commonly misunderstood. The mythical man month (MMM) book explained, an average developer is 3x the worst. the best is 3x an average. So the dynamic range is 9x, but it isn't a math so who cares. And if you are an normal developer with a friend who 3x faster, it is a career guy in a company you would not touch with a long stick, that makes you average and your friend 10xer.
This misunderstanding makes people say 10xers are rare. They are not. People who are 10x better than you are rare.
I am not that person. I am an average guy. I meet devs 3x my inferior, and 3x my superior. So I do think 10x range that MMM talks about is possible.
My second problem with the article is unit of measurement question.
It is very clear what it is. A time to completion of a well defined task by an individual developer, with predetermined level of quality of the result.
The problem is in the measurement. To measure you have to waste resources giving same task to many. And quality measurements are imprecise.
MMM book was all about the time to completion. Obviously nobody counts lines of code. Why even bringing it up?
While I think 9x range is possible, I have never seen it in real life medium size teams. (I am a short term projects freelancer, so I see two companies a year over last 18 years) The reason being, my theory goes, a contextual one. Start-ups ship buggy code fast. A fab automation company might test a released code for a year before shipping. I believe it isn't the issue of A players hiring A players and B players hiring C players. It's just the goals differ. I was faster than most at a certain client of mine, but my code was less reliable. That was fine for a specific task I was hired for, but not for most what they do.
My third problem is that the article tries to fight the notion of importance of hiring 10xers. In many cases individual performance meters less. Imperfectly studied as it might be, 10x performance measurability beats other metrics of what makes a good developer, and a good employee. How do you measure ability to communicate, motivational power, leadership, and plain good taste? So for established companies 10x hiring is not as critical.
And yet, I can clearly see why start-ups are focused on 10xers (ninjas etc). In start-ups individual devs have more autonomy, by design. Winner-takes-most aspect requires short time to market. Delivery times matter much more then quality. That being the case, hiring an obnoxious jerk who codes like hell makes clear if perhaps a temporary benefit.
So if you agree that for a startup time to market is a key, and individual developer relative importance is high, a logical conclusion is makes sense to search for (and overpay) the best. Just like it makes sense to fire 10xers once startup gets traction and replace with normally paid, normally performing guys that function great as a team.