The Complexity Of The \"Nightmare\" (Dying Light)

It is normal that this complexity at the point of death burn not all experience points? Kind of like to merge all to zero, but in fact only points of survival and a certain number. As it should be? And why in all the trailers of this complexity was discussed what will happen as I have described above?
Talking about the main game on the complexity of the Nightmare (from 3 difficulties: Normal, Hard, Nightmare).