Thinking about it, I guess this bit of knowledge probably does get subsumed into "don't move a person who might have a neck injury", so perhaps it shouldn't surprise me that more people don't know it. Argh double negatives.

Having said that, the big piece of irony in the fic is that the motorcyclist does end up paralysed from the waist down. And the hospital staff praise Harry for taking the helmet off to do CPR, when you can do CPR through the visor. Lol bad research.