A third baseman needs to set his feet before he throws. If he throws off balance, the throw will likely be errant.
It's easy on the easy plays. But when the play will be close, a third baseman still has to set his feet. Or he will throw wild. He can rush the play, ok, but he still has to set up or it will go wild.
Rosales, as an example, would always set up before a throw. His throws were true. Even on the close plays.
When rushed, EE's instinct is just to throw. He doesn't tend to take the extra time to set his feet. He gets the throw off quickly, butis off balance and it doesn't go straight. That's how I see it.