did anyone actually van surf or urban surf in real life

It's possible but I don't think there would be any document ed proof of it.

A kid in my high school did. But he's dead now.

My buddy was desperate to van surf so I got him up on top my mini van. He almost killed himself. You don't have to go fast at all to quickly lose your footing up there. And yes, fully inspired by the movie.

I'm skeptical it was a form of mainstream daredevil recreation before the movie, but for sure folks must have done it from time to time.