I have always taken "full-size" in this context to mean that the area of the landing surface on the top of the keys to be the same as on the desktop offerings. That said, there is a bit of cheating in that the height of the top row of keys on the 11" Macbook air is definitely much smaller. Not sure if that's a big deal. The horizontal and vertical distance between key centers seemed comparable to my iMac's keyboard, though.
I remember a number of times being attracted to the ultra-portable Fujitsus and Sonys of the world a few years ago and being totally unable to type effectively on them because the keys were so close together that my fingers kept getting in the way of each other when typing.