I would be interested to see an example of a before and after on this. I do think LLMs as editors and rewriters can be useful sometimes, but I usually only ever see them used as a means to puff out an idea into longer prose which is really mostly counterproductive.
I think it can be useful as a tone-check sometimes, like show me how a frustrated or adversarial reader is going to interpret this thing I'm about to send/post.