I think it's fine to have an llm write a first or second draft of something, then go through and reword most of it to be in your own voice.
With LLMs this is less clear, you don’t get the old school artifacts, instead you get hallucinations, and very subtle errors that completely alter the meaning while leaving the sentence intact enough that your reader might not know this is a machine translation error.
Quite frankly, while having an LLM draft and rewriting it would be okay, I do not believe it is reasonable to expect that to ever happen. It will be either like high school paper plagarism (Just change around some of the sentences and rephrase it bro), or it will simply not even get that much. It is unreasonable with what we know about human psychology to expect that "Human-Rewrites of LLM drafts", at the level that the human contributes something, are maintainable and scalable; Most people psychologically can't put in that effort.
The purpose of written language is to express your thoughts or ideas to others. If you're synthesizing text and then refining it you're not engaging in that practice.