Throughout It (2019): Chapter Two there is a running joke where people keep making fun of the ending of Bill Denborough's book. This is brought up by the people making the film of the book as well as Stephen King himself (in his cameo).
Is this a kind of in-joke? Was Stephen unhappy with his own ending of It? I ask because of course the movie changes the ending of the book (just as the producer in the movie was proposing to change Bill's ending), and of course there is the infamous sex scene which would understandably make an author squeamish and was thankfully also left out.
So my question is, is this joke in the movie a reference to the ending of It itself?