I wish the rear of the shell would have been more vertical to mimic the line of the cab. I'm also interested to see how the shell blends the vertical sides of the cab to the slanted-to-the-top rear end.
I think what they're referring to is the Occupant Classification System. It's what tells the vehicle if there is a person (or heavy object) in the seat. It's mainly used to turn on/off the passenger airbags.