I don't think they're basing that on anything provable. We have a hard enough time defining intelligence in people. How would you define intelligence for a reptile, and then say that a king cobra is more intelligent than a Galapagos tortoise or a Komodo dragon? I don't think their brains are any bigger for their body size than the brains of any other elapid or colubrid. I mean, many keeper say that they're smart, but in a factual record book, it's kind of dumb to single them out as the smartest. Out of curiosity, does Guiness list the world's most venomous snake? The one record Ophiophagus does hold undisputed is that of the world's longest venomous snake.