Maybe it's not a contradiction, maybe both explanations factor in. Actually, now that I think about it, hrudey's explanation does make more sense, so you can disregard mine. The game engine code is immensely complicated. I try to study it whenever I can but to say I know every bit of it's inner workings would be a big fallacy. In cases like this I can only make educated guesses, but I'm not afraid to admit that I may be wrong.