Not even close :) It's really, really good at making natural-sounding prose if you demand it, set clear guidelines (ideally a script it can run with grading, but...), Fable in particular is eerie about mimicking prose style. Try RFC style if you want really clear architecture documents with MUST/SHOULD etc.

It will, of course, be slightly worse at the non-style task (i.e. make the readme worse), but if you care about the style, that's probably an acceptable tradeoff.