Factory rear defrost 67 fastback

Yes I'm sure....well pretty sure lol. The long "resistance" wire appears to be same length as the ones in the links above. It was there when I replaced the original pass side courtesy light harness(fuel sender also)
Also when I replaced drivers side courtesy light, tail lights and trunk light, the rear defog wire wasnt there. The factory switch is located far lower left of dash. I haven't traced the power from switch to fuseblock, but 99% that's what feeds switch, then from switch along g bottom of dash over to pass side.
Sorry....long winded again lol.
I have never seen one of these installed. Are you sure of the routing? I am surprised that it is not routed with the main loom, across the top of the gas tank and following the loom down the drivers side. Maybe that would take up the "extra" wire you have. Does it get power from the fuse block?