I'm on the fence with a fold up for the same reason.Watching the video, it appears to fold up against the tailgate small enough to use the back seats.
I like the design of this, and the Seizmik, but I use my machine to haul firewood from the woodpile to the house. A folded up bed extender contraption would get in the way and cause much profanity.
In the mean time, I'm using a nylon truck tailgate (the webbing kind) as a substitute.
You have to make sure things are tied in, but it works.
And when I am done, it clips off in seconds.