The trouble is clubs often use contracts to protect the value of the player with the intention if selling. There's a good chance he signed it with both him and Levy presuming he would leave at some point during the contract, but he agreed to a longer one so Spurs would get as big a fee as possible for him.
Obviously I don't know what has gone on behind closed doors at Spurs, but I would gamble that it is more likely that Levy, who has a history of being a complete cnut, is being the cnut in this instance than Kane, who has a history of giving his all for Spurs.