The biggest thing that's come to light is that the desert stage we've been calling Dust Hill wasn't actually Dust Hill...but Sand Shower. The proof of this came from old design documents and interviews we've had since 2001, where it states that the Desert stage's past was Rock World. Add that with the maps we have, and that makes the stage we called Dust Hill actually Sand Shower. Dust Hill is something else entirely.
The time line I posted before was incorrect, it's actually:
Green Hill - Present
Chemical Plant - future
Hill Top - past
Dust Hill - ruins
Dust Hill as a ruined Green Hill makes sense. Dust doesn't mean sand, but ashes. So badly destroyed there's nothing left, only "dust".