Yeah, so many things that can go wrong in the system. Hitch pin can break/fall out, ball could break/fall out, socket could come off ball...
Neni, usually the chains are mounted back about 1' on the tongue, either welded or bolted in place. On the vehicle they attach to holes beside the receiver so they're completely separate from the ball system.
The entire hitch assembly, or the entire tongue on the trailer would have to come off for the system to separate!
I see the advantage of the system.
I've lost my trailer since the hitch wasn't attached to the ball but laying ON the ball, my bad. Since then I double check that.
Have many friends pulling horses many years and only heard of one case when the trailer came off due to a system defect. Guess, it's not happening a lot... Trailers need to be approved every second year to refresh the street permission. How's the frequency at yours?