This is what the pyramids used to look like. They were covered with polished white limestone and had a peak made of pure gold.
(lemmy.today)
Not sure I’d call that author mainstream.
I wouldn't either. It was the first link that had documentation about the physical layout of the portcullis refuting the claim that it could be climbed over.
your only way in is to tunnel through
Which is what was done in the Great Pyramid too!
My understanding is the mainstream theory is that the portcullises were resting on wood or stone supports that were set into slots in the floor during construction,
This is a good overview of the portcullis:
https://www.youtube.com/watch?v=SL_kX0FJ1cw
Notice that the rope rollers were designed for one time use. Once used, they would roll out of position and become useless.