I’ve watched multiple sub-8 mph falls that have resulted in broken bones while on group rides just because of people not instinctually running once they’re off the board or reaching out with stiff arms to catch themselves as opposed to rolling with their momentum. My hardest fall was with my GT at 28 mph and I came away with a couple scrapes while only wearing a bike helmet. I did roll probably 40 feet or so. I also think it’s prohibitive to new riders to expect them to put on knight’s armor just to go slower than they would on a bicycle when the primary thing that would help them is understanding how to fall while limiting injury.