Body tethers were mandatory until Johnny Gray tried to blow the body off, but instead the body just crumpled and left the firewall right in his line of sight. They've since become optional...
Funny cars have a long L-shaped slot mounted to the tree on the chassis that a main cross bar in the rear body tree slides into. Effectively creates a hinge so they can lift the nose of the body without pulling the whole thing off. The parachute lines are attached to the chassis under the rear end, if the body was to fly completely off, the parachutes would come out of their packs on the body since the lines are still attached to the chassis. With Cruz' deal, you can see the main cross bar is out of the chassis mounts, so the only thing I can figure is that he had body tethers holding it in place. See the hook just behind the right side tire? That's where the rear of the body mounts. I can't believe that the only thing holding that body on are the front hooks.