TL;DR:
[h=2][/h]"Tire pressure does not significantly affect your bike’s rolling resistance, but the casing construction of your tires does. This means that you can ride lower pressures without going slower, and that wide tires are no slower than narrow ones – as long as they have similar casings. The fastest tires have supple casings that consume less energy when they flex, and transmit fewer vibrations, creating a win-win situation. These tires roll super-fast no matter at what pressure you run them."


this sounds very logical to me and dovetails nicely with the claims made regarding big apples on Balloonbikes - the principle.