The other big difference between simulator training and flight training is that simulator training is (usually) conducted as a two crew procedure. The trainer operates the simulator from an instructor station behind the operating crew - leaving both able to concentrate fully on the training.
In a two crew engine failure exercise (or real event), both crew members work together to achieve the best result. Should the PF mishandle slightly, the other pilot calls, and if necessary corrects, before the situation gets out of hand, They help each other to to best extent possible.
In a flight training exercise, one pilot is under training - and the other is conducting the training. When the failure exercise takes place, the pilot conducting the training is constrained not to help, but to assess. The pilot conducting the training is at the same time distracted from the events by the requirement to adjust the power levers, retard them and then set zero thrust and monitor engine parameters. Should a handling error occur, the pilot trainer has a performance pressure to allow the error to develop somewhat before attempting to take control and thus "failing" the student.
This makes the flight training exercise more difficult to perform than the simulator exercise, as well as having a terribly higher consequence.
The training value compared to the simulator is also lower, due to the somewhat artificial crew roles required by the flight exercise.