It seems to me that if the pyramid blocks were cast in spme sort of concrete like mixture, there should be evidence of a texture left by the forms, just as one can see wood patterns in today’s board formed structures. Even if the exposed outer surfaces were worked afterwards to leave a smooth finish, some inner areas should have been revealed over time to show telltale evidence.
There is telltale evidence in the form of the bits of shells and such, the way they've settled toward the center of the Earth, and of course, the blocks fit tightly face to face. Looking for the grain of the wood from the forms might be a good thing to do.