As I taxi to a gate, I'm not even turned into it yet when the order to "cut engines" is given.. What do they expect me to do, coast into the final parking spot?? 
Doesn't happen, the marshaller will give the cut engine signal only after you reach the correct STOP position. Reading the chapter in the manual called
Understanding the STOP position at pages 50-51, would help understanding what can affect its calculation, how can be customized, etc.