Heh. For your examples there I'll refer you back to my point about a drawn map with lots of empty space not requiring physical geometry.
Anyway, no need to get your knickers in knot over it. Its not like I denounced the game for including those areas (not that I'd have thought you'd care either way about my opinion). The game is full of invisible barriers which annoy the hell out of me, and when I decided to go see what was on the other side it simply raised a few questions. If you want to hear about genuine complaints I have with the game I have plenty of those lined up.