Ed Boon said they try to make the fatalities unrealistic...
Unrealistic in a way that can't be easily imitated, is what he meant. Like Geras' fatalities, or D'Vorah's.
Though, I wonder why they need such accuracy in the violence. If the ones working on the game have to go through this for this accuracy, then what is the game doing to the players that play the thing. Some of the fatalities in the game are disturbing.