It may not have been the factory seat. Plenty of people remove the back seat and then the next owner installs a seat of some kind. If the seat was a factory seat attached to the factory mounts they are perfectly safe because Chrysler must meet FMVSS.
Retired my 94 YJ 4cyl 5spd @ 200K
Now in a 04 TJ 4cyl 5spd CV @120K+
Both as a commuter vehicle in NW, NJ
April 2012.downsized and now a 99er.
was the seat back in the upright position. if not I can see this happening if it was and install correctly I do not see it happening. when my seat is down and I go over a bump it lifts and slams back down scare the crap out me almost one day.
That is only when the seat back is down when it up it does not move at all.
I know a guy who rolled his Jeep about five times on the highway (in one sitting).
He survived, the Jeep was totaled, but the back seat was still in it when we went to the scrap yard to get his stuff out of it a couple weeks later.