Class consciousness and The Chicago Manual of Style

When I send proofs to an author for proofreading, my cover letter says something along the lines of “No changes should be introduced at this point other than the actual correction of actual errors. This is not the time for rewriting or for mere improvements; it can get expensive and time consuming. (I understand that there is nothing ‘mere’ about an improvement, but the time for them has passed.)” Or words to that effect. Nevertheless, most authors improve (in their opinion) the wording at the proofs stage. When assigning responsibility for errors in proofs, my employer uses the abbreviations that appear in The Chicago Manual of Style (16th ed.), section 2.131:

PE (printer’s error--the customary term for what is generally a typesetter’s error), AA (author’s alteration), EA (editor’s alteration), and DA (designer’s alteration).

Is there some sort of class distinction here? The tradespeople (unlike improvements, they can be considered “mere”) engage in errors; we professionals make alterations.

A recommendation, if I may. Let’s let our abbreviations acknowledge that even intelligent professionals, such as the authors we serve and even we our very good selves, commit errors. (The manual does acknowledge this, describing AAs and EAs in 2.131 and 2.132 as errors that need correction.) It would be an honest thing to do. It might even make the authors a little bit more shy about introducing changes in the proofs stage if they were asked to label them as errors. Not likely, but possible.