They would fail due to poor quality or overloading or both.

I would suggest just not strong enough however how strong do we need. My 03 Focus broke on the right side when I was stopped and rear ended by a vehicle doing 80 KPH. The collision left me in the back seat in la la land but my body received a violent twist that did plenty of damage. Had the seat let go on both sides of the locking mechanism I may have damaged my neck more than what occurred. Had it not broken at all I may have escaped relatively unharmed as the head rest could have prevented some injuries. I have presented several options and theories for thought and comment..

Crikey Roy! Sorry to hear about your experience. Are you on the mend now?

We don't think much about the seats in our cars normally, but they are part of the whole safety package. You wouldn't want your seat belt letting go in a forward collision either.

Last time I encountered a busted reclining ratchet was in the 70s and I fixed that with a welder. Couldn't recline anymore but it also didn't collapse.

I wonder what the OP's objective is?

Thanks for kind comments. Happened Two years ago in June still recovering, lot of problems with hips and pain in legs but not one to lie about. I keep wondering what if as to how the seat broke. It was a tremendous hit and left me in back seat on left side tangled up in my seat belt mechanism. Worst part is I saw him coming at last minute but no place to go, not that I had the time. I have never had a car pushed out from under me like this incident.. Great to be alive not to battle the ins. co.