You've entirely missed the point. A proofreader, like an english teacher, can return you your writing simply annotated and marked up, with suggestions and edit

You've entirely missed the point. A proofreader, like an english teacher, can return you your writing simply annotated and marked up, with suggestions and edits in red pen for example. Then you rewrite your draft into a final using those edits and notes as suggestions. Making an LLM act like that proof reader would likely not cause your output text to be labeled as generated, even by this system.