Oh, fair enough -- you are correct compared to 5950x. I was mentally comparing my personal experience with 7950x. Yes 1.7-1.9x seems fair for a bump from 5950x to 9950x (albeit at a higher power draw).
The author used kernel compilation as a benchmark. Which is weird, because for most projects a build process isn't as scalable as that (especially in the node.js ecosystem), even less after a full build.