It's amazing to me how little he cares about facts.
It's not like the pyramids are gone, they are still here, and you can go inside them. So he could easily go there and check, in which case he would find that they are almost solid stone, with no room to store large amounts of grain. Or he could simply check the internet to find that same information.
But he just does not care about reality, all he cares about is what is written in his book, and he's willing to ignore everything that contradicts it, even things he could see with his own eyes.