The exceptions are small, compared to the number of lives saved.
People used to regularly get impaled by their steering wheels or have their heads crushed against a spidered windshield. Guys who get 'thrown clear' would often break their necks, or get rolled over by the vehicle they were thrown from (this still happens a lot on farm tractors).
So, yeah, there are exceptions, which often get over emphasized in anecdotes. But I don't know of many folks who were hurt because they had their chain brake 'on'.
Philbert
I was the first on the scene of a fatal rollover, where my parents moored their boathouse, had been a log Dump site in the past, and some of the machinery mountings were still in place. one night some Friends and I were down at the river, and there was some horrible noises in the parking lot, and a bunch of gravel and debris came flying off the cliff, we went up to the lot double timing it, a car came around the curve too fast, and rolled through the parking lot, a kid of about 12 years old was thrown out of the car, and would have been amongst the gravel and debris splashing into the river, except that one of the bolts still protruding from the stone, impaled him at the base of the skull, stopping him right there, probably wouldn't have made any difference in the end though, chances that he would have survived the fall to the river wouldn't have been much better.
The driver was also thrown from the vehicle, he survived, but his toes were pointing forwards, over his shoulders, from BEHIND him, not surprisingly, there were plenty of Beer Cans scattered around and in the car
We went back down to the Boathouse, and I sent my friends back up with some blankets, while I called 911 through the Marine operator via VHF marine band radio, as the house had been moved from it's normal slip for remodeling work, and didn't have a land line connection, and this was before cell phones were anything more than **** Tracy's fabulous watch.
Unfortunately, the Kid was DOA, and the drivers injuries were more than we had the skills or supplies to do much for him, but that radio call got a Life Flight in the air, and on scene PDQ, I never heard how the driver fared, should have survived, but I would have to imagine that he spent some time as a Guest of the county for the Kids death, but having to LIVE with that would be much worse than any time spent in jail,
Doug