When you do a pool shock, you are raising the level of the free chlorine by adding chlorine or non-chlorine chemicals to the water. The chlorine level needs to be raised to the point where algae, chloramines, and other bacteria and contaminants are destroyed.
Just because a pool smells strongly of chlorine doesn’t mean it is clean. In reality, when a pool is clean, it is virtually odor-free. If the chlorine smell is strong, that is a sign the water is improperly treated.