The other variable, is that in many instances, the people operating the chipper aren’t the brightest or best trained.
My first day working urban forestry, I had a colleague (dumb as a rock) become entangled in russian olive branches and almost get pulled into the chipper. He panicked and started playing tug-o-war with the chipper. I hit the reverse lever, and he was fine, otherwise, he would have been minced.
If I were boss I would bring some military discipline to the chipper, make sure that it is a seperate part of the general busy activity and requires focus and procedures aimed at that specialized machine.
Guys get overly familiar and reckless over time.
There is a huge reverse lever/bar on all of these chippers.
I guarantee he reached into the throat of the thing. Which is exactly what you should never do.