As I posted over there today, the tape in the photos appears to have been applied to the underbody, not to hold the body cushions to the subframe; I'd guess Fisher Body applied it over the two rear subframe mount bolt holes to keep water out of the body during their in-line 3-minute water test, which had nozzles under the body as well as on the outside. They also had large foam masks that clamped in place over the heater and blower holes, steering column holes, and floor shift holes, as those parts were installed later by Chevrolet.
