Count me as "impossible" to believe.

Either some of the details are wrong, or the outcome is wrong.

Consider if someone were going across a hay field in a hopper bottom semi @ 80 mph. You are riding on the back perch. Then you decide to jump off from the side....still @ 80 mph....from 10' in the air. You have a crash helmet on....but no other protection.

I'm guessing that person would no longer be posting here.

2nd thing...if you ever get a chance to sit in a crop sprayer, do it. Then buckle up the 5pt harness & think about "jumping out".

I don't doubt that you're relating the story correctly, I'm doubting the circumstances. I also can't think of any pilot that would "jump out" from his plane & let it go wherever. I'd say if it was riding in ground effect & couldn't get altitude or airspeed, they would pull the dump lever & get rid of a couple thousand pounds in a few seconds. Maybe I just don't get it though.