Ron...
I've heard that "turn the hook and the line can't back-lash" story too. I've also had people look me right in the eye and say that heavy cable won't whip when it breaks. I've had them tell me the same thing about chains. I wish they were right. I wonder if they'd be willing to bet their life...or the life of someone else...on those theories being true in every case. They may not realize it but that's what they're doing.
I've seen both line and chain break under tension and the results are all over the board. I've seen them drop harmlessly to the ground and I've seen them do what I described in the push me pull me log truck incident. If that bull line had hit a man on the ground it would have torn him in half. We always tried to have the push Cat snugged up first. He'd signal the truck driver and the driver would signal the pull Cat. The pull Cat would then move out slowly. The only reason the truck driver wasn't hurt badly was that when the pull Cat took off at high speed with line on the ground the driver realized what was about to happen and fell over on the right seat with his arms wrapped around his head. LOL...he said later that he didn't sit up again until all the noise stopped.
I guess the point I'm trying to make is that nobody really knows, or can guarantee, how a line or chain under stress will react. Maybe an engineer could give us some stress analysis facts and figures and pat us on our heads and tell us that certain kinds of cable or line or chain would be perfectly safe to stand near during a breaking event.
I probably wouldn't let him do it on my job though. I'm a long way from being any kind of engineer and my stress analysis usually consists of doubling up on lines, hoping for the best, and keeping everybody out of the way. But I remember what an old timer told me when I was starting out..."watch out for your gear, it's out to get ya".
I understand your feelings about a cavalier attitude toward safety. People screw up, that's a given, but their attitude about the screw up tells the tale. I asked the guy on the pull Cat why he did what he did and he said (with the profanity and obscenities left out) that pulling stuck trucks in the mud was a PITA, he didn't like doing it, and he was tired of it. No problem. I sent him to town.