Correct objection :)

I don't know the technical distinction, but there is a noticeable distinction in prcatice. I guess that "cheap coating" is made by gluing a film; I see this type of coating very often in budget or even not-so-budget sports (sun)glasses.

Cleaning this type of glasses in an unltrasonic cleaner will cause bubbles to form between the film and the lens.

I think the intention was (cheap (coated lenses esp. sunglasses)) though they wrote it as (coated lenses (esp. cheap sunglasses)).

I have a few uncoated lenses, such as semi-disposable safety goggles, and a few uncoated glass lenses of one sort or another, although I expect you didn't mean those.