To limit the probability that fire escape balconies onto which a door opens will be of insufficient size [area] for a person to safely step on to when evacuating the building in an emergency situation, which could lead to tripping or falling, which could lead to harm to persons.
To limit the probability that fire escape balconies will be of insufficient size to permit efficient egress in an emergency situation, which could lead to congestion at the balconies, which could lead to delays in the evacuation or movement of persons to a safe place, which could lead to harm to persons.