And I still say you're wrong...
There was no cave in Endurance (I know, that wasn't your quote, but nonetheless).
Shadows are very deceptive. They don't mean a hole, just a gap in information. You have to use reasonable intuition to infill the gap (i.e. smooth hillslopes) not unreasonable extrapolations - e.g. giant caves.
But we'll find out in a few weeks...