Um, he still believes it.
Practicality as well as historical data would make it very dubious based on ordinary considerations. One would need a miracle of space to do that (as some believe possible for Noah’s Ark). And also, why aren’t these pyramids in cities which is where the bible says the grain was stored under Joseph? That is getting well into unverifiable prophetic claims. (I’m curious if this was in an Ellen White writing.)
I think that under Carson we would be likely to get the old food pyramids (no pun intended) back....