It's interesting that the nostalgia for "pixel-perfect design" comes from a company that seems to have been on a mission to remove pixels from the user's perception for the last 20 years. First, Apple promoted skeuomorphism as the most visible difference from the pixelated look of Windows (OS X, 2001). Secondly, they made pixel-perfect designs irrelevant by making a powerful, small handheld computer. It made the goal…
So saying that the iPhone was responsible for RWD is too much credit I think.