Replacing the Air Bag module is NOT part of maintenance, so your insurer is incorrect. As far as the Air Bag Module being damaged, were there any problems with it before. If the Air Bar or SRS system was deployed, which includes your seat belts, then it is standard for the Module to self-destruct and need replacing. It does this as a safety precaution in case the module was shock damaged during the collision. I think I would call the Insurance firm and ask to speak to a manager who knows their job. I have been involved with several Accident issues and the insurance ALWAYS replaces the Air Bag Module as part of the repair if any part of the Air Bag System, including the seat belts, was deployed. The Seat Belt Retraction always comes on in an accident unless you just touch another car in say, a parking lot.