That and the fact that it gates progress entirely using a mechanic that had, up to that point, never really been introduced -- you might have noticed it on accident, but the whole design of the game (go fast from left to right, jumping sometimes) and, as you mentioned, the fact that it bounces when you jump on it, lead you to have no idea how to solve it correctly.

My spicy take is this: that particular obstacle is not "they upped the difficulty", but is instead "they designed this poorly."