That is a new display of the profile specs at the listing for the neck, but it's the standard spec for that profile, not an actual measurement of that particular neck. What Wizard of Wailing is saying is that his necks feel as though they have dimensional variation from part to part where the profiles are supposed to be the same.
The hand can sense remarkably small changes, even those that can't be easily quantified without instrumentation. I've never checked the dimensions on my necks as I've never felt a need to, but it wouldn't surprise me to find that there's a few thousandths difference from one part to the next. They need to be sanded after they're milled, and that's never an exact process.