That's because the article writers have rarely worked with a 10x programmer. They get shit done, fast, with massively below average bugs. It comes from a deep understanding of the code, the language, and the metal. They're also more likely to innovate and/or find novel solutions.
In the past they were spread around or sometimes in research (Bell), now they're clustered in the big 4 (Google, Apple, Microsoft, FB) and SF.
So unless you are where they are, you won't find them or even know they exist. That guy who can wrote a cool Jquery plugin at your startup probably isn't a 10x programmer. John Carmack would be an example of a 10x.