I'm imagining a big reason for "pressure sensitive" is that it has no thumbstick. Obviously the intent is that the left touchpad is to substitute for a thumbstick, but some stubborn gamers will insist on using the d-pad-ish buttons. So say you're playing a game designed for a thumbstick on the left button-pad, and the game requires a light-touch to "walk" like assissin's creed or Mario 64? The pressure-sensitive buttons provide that.