The Frenchman you mention is Joseph Davidovits, he actually makes sense (which is rare), and I’m neither an idiot nor a leftist.
I read something similar in Omni magazine a long time ago. The article I read “claimed” that the granite in the Pyramids is consistent with what a granite concrete would look like. It would be easier to transport ground-up granite which is “formed” the same way we build concrete buildings.
Not saying it is true considering the source but it is a reasonable theory.
You may not be a leftist, but if you think the pyramids were made of cement, I can’t vouch for the other. And I read the book. Interesting nonsense, like the first “Chariots Of The Gods”.