That negligible difference is actually a fairly large one once the physics of inertia and impacts gets into play. The energy, and therefore the damage, is exponential based on velocity. That ≈6.6km/hr difference increases damage by a lot more than you may suspect, and pedestrians don't generally wear helmets and pads to protect themselves from impacts.

If I'm not mistaken, class 3 also has a throttle vs just pedal assist. I think the throttle is great personally. Sometimes it's hard to get started to cross an intersection or something, and the throttle is a huge help. Feels like this kinda kills some stuff for old + disabled.