Doubtless the segue from “Big Void” to “massive chamber” is justified in the book, althought I notice that “chamber” has scare quotes around it, where it first appears in the synopsis.
https://www.innertraditions.com/books/the-great-pyramid-void-enigma
No such reticence in the excerpt, where I find eleven (11) instances of “chamber” (and none of them scare-quoted).
https://www.innertraditions.com/books/the-great-pyramid-void-enigma#excerpt
Doubtless Creighton is safe for some time from having his surmise empirically refuted.
M.