He’s pretty serious! Travers hated the film so much that in the 1990s when the stage musical was being planned she stipulated that no one involved with the film take part.
She hated it all the way to the bank.
I’ve read the major Disney bios and well before this movie (which I haven’t gone to see yet) I read the New Yorker article. So I am familiar with her opinions disagreements.
I liked how she complained of how they turned Poppins in to a “soubrette”.
Harlan Ellison a nothing to do with anything.