I DONT think Utai took a deliberate dive, however I DO think he did play it for all its worth, but in saying that, a lot of players do it, Broncos do it, Roosters do it, Raiders do it, everyone does it.
It was because Morley grabbed Utai by the throat and pulled him down that Utai was forced to hit the deck; otherwise, he was off downfield for a try. You don't dive if there's a chance you can score.