Yes, you can go very fast on hills riding traditional bikes, which is why hills are dangerous & most cyclists handle them carefully.

Ebikes can cruise @ relatively high speeds even on flat ground.

I honestly think most folks haven’t had a cycling accident since they were very young & don’t realize how brutal they are as adults.

EDIT: Just as an aside, people that ride those motorized single wheel things are friggin nuts! Imagine crashing on one of those goddamn!