That would actually be a reasonable thing to do with a model that is good at writing though. I'm sure if you used that method on Opus 4.6 you'd get a pretty decent result, because Claude models used to be quite good at that sort of technical synthesis. Asking a model that is bad at technical writing (e.g. Opus/Fable 5) to write your docs is a bad idea.

Ultimately what seems more important that how good the model is at task X vs task Y, seems to be that the human accepting/rejecting/iterating on the text can actually identify "good" from "bad" text, and makes the effort to fix it. Otherwise it doesn't matter much what model you use, it makes boring, bland and bloated prose.