In the pictures of the half shredded painting you can see that the shredded portion has what looks like a kink where it may have been around a roller or at least a non straight path. I doubt the paper that is shredded is the same as the one displayed in the frame. I suspect it is rolled up inside the frame and a second one is ejected. Also from the side view it doesn't look to be directly well lined up as it should be if it was ejected straight out past a shredder.
I agree that is the most likely situation. The assembly video shows the blades aligned at a right angle to the paper path which would never work. Maybe that was just part of the planning and the final configuration was different but the video does not show it.
An alternative, assuming that the blades were oriented correctly, is that the lower part of the canvas was preloaded past the shredder blades for reliability and therefor started out wrapped around the lower roller.
The paper colour looks a bit different too.
That part of the canvas would not have been exposed to light for 12 years.