I have considered that as well. It is very possible that such a secret exists, and we just haven't found it yet.
The existence of this PD72-extension makes me wonder if there may be other PD-extensions hidden throughout the game, only accessible through Mirror Mode. We should start an experiment ... anyone who has Mirror Mode on the other servers can enter as many PD's as possible and hope for

's on the later levels. Eventually we'll be able to discern whether each PD leads to another secret, or just back out into the well. There is a good chance one of these PD's veils the Inversion Key (or the innocuous 353rd item in some other form) !!
