You realize, I hope, that Icahn is speaking publicly like this to try to force Apple to increase the buyback.
He is not a friend to Apple. Icahn has purchased a billion dollars worth of Apple stock. He wants the value of that stock to increase by some significant percentage (20%, 50%) very quickly, so he can sell it and make a buck. If things don't go his way, he'll do anything to Apple to force the issue. That's how he operates. He's not about creating long-term value or companies that are healthy over the long term.
By publicly creating the hope and expectation of a bigger buyback, he increases pressure on Apple to make a bigger buyback, whether or not that's fundamentally good for the company. Icahn creates the possibility of shareholder discontent in the absence of an increased buyback.