There may of been some electrical fault years ago (when the car was still valuable) that required a replacement, newer spec harness. I've run across that a few times, though never in a Rover.
I've never seen it on a P6, although I'm sure it happened, but as for Rover in general, during my time at the Main Stealer the electrician fitted loads of new looms under warranty to SD1s after the looms were fitted jammed behind the heater unit at the factory.