Any good heli sim will have an underlying physics model that gets the device a majority of the way to the correct behavior. The flight test data is then used to confirm correct simulator behavior, and if necessary tweak the simulator physics model to achieve a data match.
The black magic and art of creating a good heli model resides in the ability of the engineer to tweak the physics model using the flight test data without introducing incorrect behavior in the flight regime where no flight test data is provided.
These days, our ability to simulate helicopter behavior is pretty respectable. So while the sim might not be perfect, it should be accurate enough to give you some sense of how to survive an emergency situation in the actual aircraft, regardless of whether that situation has been validated by flight test data or not.