You could extend that logic: Since I couldn't code at some point in time and I can now, I've become infinitely better at it.
Compared to someone that can't code I'm infinitely faster in theory. Do note that in reality, if someone that can't code needs to write code, he'll likely learn to code first. However, once he learns to write code, he is no longer someone that can't write code.
The 10x programmer isn't 10 times nothing, of course. The 10 times rule is, I think, 10 times better than average. So we have to know the average first.
The amount of programmers rises very fast: IIRC, the amount of programmers doubles every 6 years or so. The average programmer therefore has 6 years experience.
The 10 times programmer has to be 10 times better than that. How is he 10 times better? He has to be able to beat a 10-person team of people with 6 years experience on average. That is a team of 4 juniors with 4 years experience, 3 "medium" programmers with 8 years experience and 2 senior programmers with 10 years of experience.
Imagine a contest where you have to develop a huge SAAS management-like system. One team has the 7 developers described above. The other team is the solo mythical 10 times developer.
Well, I think the 10 times developer is going to have a head start, but he's going to burn out within 2 months, releasing nothing and starting a new project somewhat later. The project manager now has to find a new 10 times developer, but he finds out that no-one can replace him and they need to start over.
Meanwhile, the 7 developers are playing table-tennis and having boring meetings and finish the product much later than planned, but it is done and it sells fine.