That kind of talk can be useful in certain circumstances. I was directly behind a car that suddenly turned into the guard rail (instantly destroying the guardrail and the car) a few years ago. I slammed on my brakes and got out fully expecting to be the first on the scene of a fatality but it wasn’t quite like that. The driver was injured and semi-conscious but the airbag had done its job while knocking the hell out of him and injuring his face and nose. He barely knew what was going on and started to go into pretty severe shock with uncontrollable shaking and incoherent speech (I think he just fell asleep at the wheel but the accident was very violent). That can be dangerous on its own.
I couldn’t find any life threatening injuries so I just called 911 and stayed there talking him down in the most calming voice I could while the police and ambulance arrived. I really think it helped. I convinced him to stay in the vehicle and that other people were going to take care of everything. Even holding hands seemed to help get his shock more manageable once he sort of understood that he probably was going to be OK after help arrived.
Doctors and nurses (at least the good ones) use the same strategy in emergency rooms and critical care facilities. The brain-body interaction is complex and not well understood. It is often better if you can keep someone calm and focused on something other than their own trauma.