You are completely jumping to the conclusion that when the author says "10x better" he means some dimension that you do not care about.
Programmers care about productivity too. And when somebody puts a number as in "10x better", that is usually the metric they are talking about. (Although this one seems so fuzzy that the statement is meaningless.)
I don't know many programmers who are jumping to use Haskell for their personal projects. What you use at work is usually determined by the surrounding infrastructure but at home you can use whatever you want for productivity and yet most people continue to use their favorite non-functional language. If it's really 10x better and can overcome network effects then shouldn't we see a lot of Haskell personal projects?
Programmers care about productivity too. And when somebody puts a number as in "10x better", that is usually the metric they are talking about. (Although this one seems so fuzzy that the statement is meaningless.)