Should the play have ended? NCAA rules say a runner is down if "any part of his body other than his hands or feet" contact the ground, and it sure looks on replay like his wrist was on the ground, ending the play. Dyer clearly thought the down was over! Kevin Lehde, a high school football official in North Carolina and a TMQ co-conspirator, notes that when Dyer stood up and made no attempt to advance, his forward progress stopped, and officials could have ended the play for that reason: "The rule book is clear that the runner going down stops the play, not the whistle. If Dyer himself thought he was down, I would be fine with the official blowing the play dead while he's rolling over the defender, with the explanation that his forward progress was stopped."
There's a point that announcers often get wrong. At the high school, NCAA and NFL levels alike, it's the action of the play, not the whistle, that ends the play: The whistle is only a signal to stop. If a player drops to the ground and the whistle doesn't sound, then a defender pile-drives into the player, that can be flagged as a late hit -- "late" despite no whistle, because the action of the play has ended the play. As Dyer was rolling over the Ducks' defender, Oregon's Zac Clark pulled up and did not dive into Dyer. Clark thought the action of the play had ended the play, and was avoiding a late hit. Had Clark driven his body into Dyer, the 37-yard run never would have occurred. But there's a high likelihood officials would have thrown a flag for unnecessary roughness, judging the down was ended -- though the replay booth later said the down had not ended.