What doesn't make sense? Surely it shouldn't be too hard to even say "air bags deploy when there's x amount of force, so they would have deployed in the simulation" let alone have an actual physics simulation going on.
In all of the incidents, air bags deployed. 5 of the 8 incidents were in simulation. The simulations likely have extremely realistic models for safety critical features such as airbag deployment (which relies on specific sensors in the vehicle).
Or they just looked at what portion of the car got in the simulated collision and and were like "yup, that's where the bag sensor is".