In retrospect, I think db4690 is correct and that I was thinking (incorrectly) about that issue. My bad.
Just some food for thought. Some decades ago Nissan started offering remanufactured parts. That would mean an outside subcontractor.
What if the transmission the OP received 30k miles ago was not a new unit but a reman one?
There used to be a massive Ford reman facility in OKC which shipped reman stuff to Ford dealers nationwide. Even though run by Ford they also remanufactured GM transmissions.
I knew 2 guys who worked there. Both great guys to know BUT neither one had a mechanical bone in their body.
A huge engine reman facility in OKC used to advertise in the paper for “Engine builders. No experience necessary”.
That does not inspire a lot of confidence and things like this are what forms my generally unfavorable opinion about assembly line reman places.
It’s difficult to see a new unit failing in 30k miles even sans fluid changes. A reman unit could easily be a different ball game altogether.