The author is confused. 0C is special to us because it is the freezing point of water, but that doesn't really make it special within thermodynamics -- it's just the freezing point of some arbitrary substance at an arbitrary pressure (ATP). 0C isn't even the only freezing point of water -- if you add impurities or change the pressure, you can change the freezing point!

Maybe 0K (Kelvin) is special, since that implies zero gas entropy, but 0C doesn't have any magical properties.