Skull cavern button

[Crater]

"Added a skull cavern statue that can be used to toggle hard mode in the skull cave (after completing Qi’s challenge)."

When I try to press the button it just says ? on top of my character. Why is this? On this save I have finished the challenge, and went to sleep to "update" the save.

[Lowly Tarnished]

Same thing for me. I really wanna know what it does.

[NBOX21]

It just toggles between the normal and "hard" version that is normally used during Qi's challenge when inside the skull cavern, similar to how the shrine at the bottom of the mines works.