The purpose of the big hole in one of the corners is to show that the mechanism of the puzzle is deeper-than-origin. However, only two deeper-than-origin rotations are enabled (two screws at the inside). Some shallow rotations are enabled too (screws visible at the outside), but not all. This makes the puzzle confusing to solve, as sometimes rotations are blocked. The screws are kept visible to reduce that confusion again.
There is something paradoxical about "deeper-than-origin". This puzzle is deeper-than-origin, because only some of the cuts are deeper-than-origin. If all cuts were deeper-than-origin, then the puzzle itself would no longer be classified as deeper-than-origin. Strange, isn't it?