It's probably unprecedented for a filmmaker simply to take the writers' script and treat it as the instructions on the package. What really happens is you pretty much suppress your own instincts - and your own views on the matter - and write things the way filmmakers would like to have them, though the filmmakers often don't know what they want. They can only find out by reading what you do.
Tom StoppardI never had any frustration about writing uncredited. I always felt that the satisfaction of doing it was in the doing of it, really, and getting recognised by the small number of people that know what you did.
Tom Stoppard