From the creator's PoV their intention and quality is defined in post-production and mastering, color grading and other stuff I am not expert on. But I know a bit more from music mastering and you might be thinking of a workflow similar to Apple, which allows creators to master for their codec with "Mastered for iTuenes" flow, where the creators opt-in to an extra step to increase quality of the encoding and can hear in their studio the final quality after Apple encodes and DRMs the content on their servers.
In video I would assume that is much more complicated, since there are many quality the video is encoded to allow for slower connections and buffering without interruptions. So I assume the best strategy is the one you mentioned yourself, where AV1 obviously detects on a per scene or keyframe interval the grain level/type/characteristics and encode as to be accurate to the source material at this scene.
In other words: The artist/director preference for grain is already per scene and expressed in the high bitrate/low-compression format they provide to Netflix and competitors. I find it unlikely that any encoder flags would specifically benefit the encoding workflow in the way you suggested it might.