They aren't mythically smart and intelligent and can recite api features off the top of their heads.
No, the 10x programmers I've mostly encountered are "boring":
* They write solid code that's maintainable and relatively bug free. Fixing bugs is an incredibly time consuming activity. A developer who can reduce their bug rate is incredibly efficient not just for themselves but for the entire team and project.
* They aren't going to prematurely optimize in terms of code or design. How many of us have seen development grind to a halt due to an incorrect use of a design or architectural pattern? The worst grievances I've seen are using Microservices when it's not needed...leading to huge slowdowns of productivity due to overhead costs. And that's just one example.
* They understand the value of good software engineering practices that lead to long term success of the product/project/team. Many of those practices are "boring" but are necessary such as writing effective automated tests.
I guess another way to put it, many of the 10x developers I've seen are ten times more effective because they can avoid common mistakes that the average developer makes.