Dude, Oda literally said, "No, I go with the 'flow'. I cherish what 'grooves' I get into. First, I draw really rough sketches of the new characters. When doing that, I always write down a line or two with them. It just happens naturally, I don't even think about it. The first thing the character says usually helps in the long run to build his personality."
Another example, in WCI Oda literally said, paraphrasing "Sorry for taking so long, ideas just came popping into my head" which totally contradicts the statement his editor said about "WCI finishing soon" which it didn't and took another year to finish hence why Oda had to apologize. That is a symptom of an author writing out their ass and doesn't plan ahead.
Nika fruit being talked about via Who's who randomly is another symptom of an author writing out his ass. Yamato randomly being created 90 chapters into Wano without any prior foreshadowing is another symptom of an author writing out his ass. Literally hundreds of examples. It's hard to try and hide the symptoms of an author when they write out their ass, it becomes way too obvious.
So it is bad to have Shanks show up and then immediately leave just to promote a movie, right? So there are "objective measures" we can use to evaluate writing and one of those measures are don't write advertisement into your story. That should be rule number fucking 1 in writing. Make sure you tell that to your group of filmmakers.