> Developers who deliver 10x as many features inherently do so at the cost of maintainability

I don't think what you say is completely true. People who are more experienced tend to be able to produce features much more quickly than those who are junior, just because they've already run into issues before so can anticipate them or solve them more quickly. If anything I would argue people like that actually write code more quickly that is more maintainable.

I don't know if he can ship 10x as many features; I didn't think term 10x engineer was used literally. I just know I've worked with quite a number of people and he is one of the best developers I know.