Reading the article they focus on children and e-bike users. Can kinda understand it from that point, e-bikes can go abnormally fast and children are vulnerable. Would've expected the advice to also count for elderly people. I'm a 30 year old reasonably in-shape guy using a regular bike, chance that something happens to me on a bike is small and it's even smaller that I'd get really hurt by it.
Neurosurgeons have a very skewed view of the statistical likelihood of head injury. They see such injuries every day, and it can most definitely make them believe that the risks involved are much greater than they actually are.