dirkac
I smash your Boxes.
Not saying it makes sense, just saying what it likely is.
But why would it be considered Post-Game, considering that said Guide also doesn't cover a map of Sea Spirit's Den, despite it having a slide for it and more Post-Game value than the Chamber of Emptiness.
On that note, the entire lower half of Route 22 isn't documented, most likely due to the fact that you need Waterfall to access it, and that it's first accessible before the 1st Gym, and due to the Chamber of Emptiness being situated at the lower half, it would logically be discluded either because said area was forgotten about, or discluded due to it being such an old area and having a jump from before 1st to after last Gym or vice-versa us simply too large to cover without some confusion.