So I finally read Chapterhouse for a second time, and what stuck with me the most was chapter 41, which was when Odrade and her sisters are waiting in a lobby of sorts on Junction. This chapter involves robots more than any other chapter in the Dune series, and being one of the last chapters of the last Dune book, provides decent evidence that Dune 7 was indeed not going to be about robots. I can sum this up in one question:
Why would Frank turn machines into the Great Enemy when he had just finished describing machines as almost a joke?
While it was never explicitly said, Frank thoroughly set the mood that machines are simply silly things. Many of the reasons why the books Herbert Junior and his butt explorer put out do not fit is just how it conflicts with the mood of the series, straight up contradictions aside.
I'de rather not quote the chapter, for I believe the the entirety of the scene best explains what I mean. It is only the first three and a half pages of chapter 41, and is one of my favorite scenes in the series.
"Imagine being told that the forging of the ring was really not a plan of Saurons, he just helped - and it was really for the good, because it was needed to defeat these mega-spiders which were somehow related to Shelob (in a way inconsistent with the Silmarillion)...
Meanwhile, a hobbit named Norma becomes a valar because she dies horribly due to a spider-bite, returns to Middle Earth and walks around a bit, inventing everything interesting you ever hear of in LoTR."