They're built on a production line so doubtful it's a factory error, more likely a cost cutting repair
I've seen a lot of VW's with very bizzare combinations of specs in my time *, so I would never rule out factory error, but I agree that cost cutting (or simply ignorant) repair is the most likely reason for the lights being wrong.
* For example, my fiance's mk4 has half of the front seats with heating elements (drivers seat back and passenger seat bottom)
with no seat heating and there has definately never been any seat repairs or replacements on the car