Reptiles are as diverse cognitively, as any other species, in my opinion. They may not rationalize, or they may. They certainly express varying behaviors among species, and even among individuals of that species.
I have a Corn Snake, my first one, and I really think he has lost most, if not all, of his hunting instincts. He eats like a turtle, and doesn't even make an attempt to coil, or even change position while eating. I would certainly consider him to be conditioned to ignoring most of his primal instincts, and with future consistency, I don't see how later generations couldn't be completely tamed.
Now, whether I would say this Croc is proven to be tamed... I wouldn't put a dime on it. The video stated that he found the Croc five years prior, and he still must have been a big boy, thus hunted a lot of food through instinct. These instincts have been passed down genetically, and used through much of this animals life. Should he even "accidentally" lower his jaws around this man, there is no way it would rationalize releasing it's grip.
Dogs are very different though. Of course they have been domesticated for centuries, but they also have a clear need for companionship, and are of the most intelligence of any many creatures (in my opinion). I can say without any shadow of a doubt that my dog will not have an unpredictable instinct override our bond. She is connected to me unlike any other living being, and we have a great understanding of one another. Reptiles are far from this cognitive capability, and will never reach the same level of trust with humans, and train ability as dogs (at least not until they evolve into dogs).
