This is false because the one who will be at fault will be the car that stopped suddenly. The car at the back has to be traveling fast in order to hit the car. A lot of cars are able to avoid this type of accident because they are traveling at a normal speed. There are different reasons why the vehicle may have to stop suddenly.
People can give various reasons for this. For example, some stop because a person suddenly crossed the road or another vehicle suddenly crossed the intersection. Being aware at all times and having fast reflexes will always help drivers avoid collisions and other forms of accidents on the road.