That vid is a few years old.
The dudes did not attach the towstrap to anything but the bumper cover
which is why it flexed so much.

A couple of my friends and I repeated the happenings with his soon to
be cubed cavalier.  Hooked the towstrap to the reinforced lip under
the bumper cover and used my van to yank. :D  Needless to say, we
ripped the rear off like that one.  It sure was fun though.

sudhir.