I believe he means that the anti-freeze reduces the hydrogen bonding between water molecules, which actually does reduce their size.

Generally the high boiling point of water and its high heat capacity is due to the hydrogen bonding between molecules. However, Tango, you are correct that the addition of antifreeze increases the boiling point of water. This is due to the colligative properties of mixtures and the fact that anti-freeze has a higher vapor pressure than water. The addition of anti-freeze increases the overall boiling point, despite reducing the hydrogen bonding of the water molecules.

I hope no one minds my geeking out here. http://www.peachparts.com/shopforum/images/icons/icon10.gif