I would say true. The only reason that it doesn't boil in the radiator and the rest of the cooling system is because it's under pressure. This is why it's perfectly fine at over 200 degrees but as soon as you pop the cap off (don't) it will come shootin out and boil.
I never understood it at first until one day I put a bottled Mtn. Dew in the freezer. It was cold as hell but not frozen, because it was under pressure. I popped open the cap and I watched the whole thing turn to slush. Top to bottom. Kind of cool actually.
