Cayenne Seat Belt Restraint System

[trapper9]

I have a question regarding the seat belt restraint system in the Cayennes. If the vehicle gets in an accident and the air bags in front go off I believe the rear belts tighten up at the same time. I looked at one that had an accident and the rear belts were pulled in on both seats super tight and cannot be extended by hand. I would assume that they were not being worn as the front seats were shoved forward. Does anyone have any expertise regarding these?