Assuming the upholstery is original and matches the back seat, I’d say it’s an option. I’m away from home just now, so can’t check the hardcopy Chassis or Fisher Body Manuals to be sure. Sorry.
My ‘70 WC is a convertible so not applicable here. However the chrome seat trim is identical, and your lighters appear non-integral, but sit on top of the trim, so again likely an option.
Another clue might be where the power feed comes up through the carpet. Assuming you have power seats, the connector is just beneath the front seat on the drivers side. I would assume the feed for the lighters likely comes through there as well (the PS are powered by the 30A breaker, along with the other HD-type options, so possibly the lighters come off of that harness). It it all looks “factory” electrically, then again further evidence of a factory option.