it could be possible. unusual things happened to cars at the plants in the 70's.
I have a 72 roadrunner. had just short of 10K miles when I bought it. I bought it from a flipper I know who bought it from the original owner.
when I was restoring it.
I found out it was painted 5 times, including under the hood and inside of the trunk.
had a NAD PAINT tag. with a 229 spd date, to early for NAD PAINT tag.
it also had bumper impact strips when it wasn't coded for them.

after I finished it I met the original owner at a show. he told me it was never repaired when he owned it. and when I took it apart it looked just like yours. it was rustproofed by Ziebart when new and looked like it was never apart. the guy I bought it from never touched it when he owned it.