Speaking only of situations in which writers are parachuted in to do a rewrite, doesn’t the writer’s autonomy depend upon how many notes the producers already have on the script you’re picking up? Can you really be doing your version first if it comes with a set of specific instructions?
When they do the handover they’re gonna say…
“We don’t like it because of this and that. Can you fix it, please?”
And/or…
“We want it to do this and that instead?”
In the edit it’s usually a combo of both, but depending upon the personalities involved it can often begin with the producers wanting you to do specific things, rather than asking you to do your version.