Yes, while Parrott's chance was a gimme... you can't be relying on every single perfect chance to go in. And we shouldn't be saying oh no we must drop Parrott because he missed a chance. Otherwise you'd say drop Duff from the Ireland team for missing one v one chance in Paris, etc.
It's a probability game. You create many good chances and hopefully some go in. We created some good chances, but not enough.