I appreciate the concept, but I can’t help but feel that the page is loading and getting “stuck” as I fill out the form. Probably a result of the many top bar-style page loaders, but still feels a bit awkward.
Seeing it go backwards is even worse.
Also it literally makes people take their eyes off the form they're filling out to glance at the top of the screen where the bar is bouncing around, giving a nice distraction for you to stop filling it out.