I think YZF just mis-parsed your sentence, and thought you meant a thou is for very high precision work, while you meant that a tenth is for very high precision work.

(That said, I'd add -- measuring to one part in 10^6, for anything except time, is challenging but still very doable; machining to one part in 10^6, for anything beyond very simple shapes, does require pretty exotic methods or very great care, and to verify it you have to measure to one part in 10^7).

Oh, yep, there's an extra comma that makes my comment a bit ambiguous. Alas, it's outside the edit window...