I think hollowing out a pyramid would weaken and collapse it. They actually weren’t that great in terms of structural engineering... just well-placed piles of stone. I’m not denigrating the skills of the day, they were good for what they were. But they weren’t up to the task of building a large hollow structure built of stone. All those extremely heavy stones had to be resting on other extremely heavy stones. Too much hollowing and the walls definitely come tumbling down.
It’s something that could be empirically simulated on computer, I suppose. Do it right, and like a keystone arch or flying buttress, the inward pressure would keep it from collapsing.
Also, to follow on to the religiously themed discussion, Joseph might have asked for the storage pyramid to be opened up after its use had come to an end. It wouldn’t even be a pyramid any more.
Again, an experiment in sanctified imagination, and nowhere near dogma, at best directions in which investigation could be launched if it ever proves possible. The White prophecies seem at best dubious, following on to non-Christian Jewish ideas as they often do. But again sometimes nutty ideas end up proving to have a kernel of truth in them. I’ve seen enough strange things in my day that I could say this from experience.