The point isn't necessarily to reduce accidents it's to reduce serious injuries and deaths. Slowing down is safer if there is an accident.

That said I'm not convinced things like this do increase accidents. The knife analogy is suspect but potentially accurate for that very reason. This is a common saying, but my first career was as a professional cook and that common saying is a running joke and source of constant mockery in professional kitchens. People who work around knives know that sharp knives are much more dangerous than dull ones. They're valued for other reasons, not safety.