Now I think you are debating for the sake of debating. . Seriously I think he made a really valid point there.
What is the big deal anyways? Chances are if you wanted to DS onto an inpassible terrian you will scatter anyways, so wouldn't it better to just pick a place hoping you will scatter onto a mini instead?
Also just think of it this way, that if the Mawloc dosn't DS onto a unit, the unit or person, got out of the way once he felt the ground started to rumble, shake and move.
But after reading the rules, I don't see anything where DS allows to bypass the main rules. Next thing we will be saying is we will be able to Flank on top of models when we flank now. Since the rules said we have to go on what ever side we roll on or get to choose, and it dosn't say we can't go into impassible terrian as well. What about other units coming from reserve? It dosn't say they can't be placed into impassible terrian, just says that it has to come from the players edge. So you telling me that these mini's can come from impassible terrian on the players edge when coming from reserve or when outflanking as well?