I'm a bit late to this thread, but I was in a similar situation ver Christmas too.
I ordered a brand new MY17 Nismo in Storm White, on arrival we noticed a very small mark on the rear bumper and had to play fun and games of who would repair it (Nissan or the dealership). We initially got quotes in for a brand new bumper with paint etc and the cost was crazy (not our problem of course). We also got the price for a smart repair guy to touch in the damaged area.
After much deliberation we decided to get the smart repair done on the bumper, and took the car. I could have pushed for a brand new bumper and respray......but this would have been a gamble on the new paint being as good as factory paint. It is also a waste of a 99% perfect rear bumper and factory paint. Atleast this way I can't see the mark any more, and the bumper joins to the rear quarters are all done on factory/matching paint
For the OP, sounds like you got a good deal anyway as you were swapped onto a factory painted PW bumper
Glad you got it sorted.