Except that isn't the same thing as what this is. That's moving the goal posts on the argument of what he should have had in the game he played. If all you can say about his play in the game is that well he should have a .900 save percentage or more, you lose context of the game itself and what is a realistic expectation for him to stop.
That's arguing numbers...not arguing the game.
This type of game/goals being let in isn't just a once in a while occurence with stalock though. This is in the 20+ games range now that he has been this bad.