I've read most of the book while waiting for my wife in Chapters.
The list is just a "general list" based on his research, and even he says it isn't foolproof. Some dogs require more training than others, and some dogs are just easier to train than others. It's a fact. And even within breeds there can be a variance of intelligence. People seem surprised by this list, I'd say for the most part it is quite reflective of the breeds I've met.
For anyone who has spent time with a well trained Standard Poodle, you'd understand why they were ranked highly. Usually the small poodles are owned by people who treat their dogs like Paris Hilton
, hence their stupidity.
Cheers