I've seen several translations of Herodotus' work but not one of them specifically says any great pyramid was a tomb;

"The aforesaid ten years went to the building of this road and of the underground chambers in the hill where the pyramids stand; these, the king meant to be burial-places for himself, and surrounded them with water, bringing in a channel from the Nile."

[blog.world-mysteries.com]

Indeed, here it is suggested that the burial place itself was surrounded by water. If there is any accuracy to such a report the implication would be the pyramid is not a tomb and Khufu was buried at the bottom of the Osiris Shaft surrounded by water. Whatever the case it seems that most of the references to great pyramids being tombs didn't originate until the 1830's.

Manetho was likely the last person to know because he had ample original sources to piece something together. Along with Horapollo these are most of the early sources and not one is known to have said pyramids were tombs.

I believe it is very telling that no direct accounts and no direct evidence for tombs exist. This simple fact implies a tremendous upheaval between the time of construction and today took place. How else can we possibly explain how a pyramid building society neglected to leave so much as a note or word related to construction and there's nary a peep from historians? How else do we explain the simple fact the people who built them said again and again the pyramid was the dead king and his grave was in the sky? Something happened and we came to believe that pyramids could only be tombs so it's not even open to question for most people.

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Man fears the pyramid, time fears man.