You're right, the ideas used are flawed. But then, so is most people's idea of "intelligence".
There's an obedience site where the man lists dogs who are difficult to train - and GS are 1 of them, e.g. People equate "intelligence" w/"obedience", but it's not the same. A dumb dog can be very obedient, a smart dog take ages and lots of muscle to train.
GS are usually very stubborn, but that is not the same as stupid (just look at the old "mule" insult - but they're not stupid though they've been called that for ages, just stubborn and don't want to obey you - sometimes for good reason). Not at all. I know my former GS was smart as a whip - outsmarted whole slew of Border Collies in their own home, apparently understanding their home better than they did - but somewhat stubborn (she was a dominant dog). She also knew what to do when I asked her to look for my cat who had gone into shock and escaped in a strange area. Actually she overall didn't take much effort to obedience train, but she did need the "muscling" to do it by and large.
It's as what I say about the human world - there is "intelligence", and there is "knowledge". Repeating the whole encyclopedia is not intelligence, it's having knowledge (and good memory). Intelligence is how you use the information. Same w/dogs - where training = knowledge.
I think "trainability" is an important consideration, because it generally gives novice dog-owners a good indication of how cooperative a particular breed would be. But this list is still deceptive because you sure wouldn't want to turn your average Border Collie over to a novice dog owner (talk about a disaster!) Very intelligent, very trainable, but also obsessive compulsive workaholics who will make your life hell on earth if you don't give them a job to do . . .
Better not to rely on a list, just talk to dog trainers and breeders before you buy!
-- although I still think the Afghans are about the dumbest dogs I ever saw.
Stubborn, you bet. Mean, you bet. Hold a grudge, absolutely. But never, NEVER stupid.
(of course, my family is from the country in the South and we actually know mules. I prefer horses because I like to be sure that my steed is dumber than I am . . . with a mule you're never sure.)