Confidently asserting that there hasn't been a crash involving a commercial flight with few survivors in living memory and your examples are all post-2010 fligh

Confidently asserting that there hasn't been a crash involving a commercial flight with few survivors in living memory and your examples are all post-2010 flights is...certainly something. There are plenty of people much older than 20-30 years still kicking. And you can get a hell of a lot more than a bruise from a seatbelt due to the magnitude of the forces involved in a plane crash, especially one that [allegedly] killed almost everyone else. Seat belt syndrome is a well-known thing. The GP's story may or may not be true but your points for it being "extremely unlikely" don't hold water at all.