Thanks for the reply.
Now it gets more interesting - In case I change region from Germany-English where i still get:
J0 JN0 C0 D0 Z0 ZN0 P0 PN0 R0

to US-English I get (same as you reported):
J8 JN8 C8 D8 Z0 ZN0 P0 PN0 R0

So, we can add to your list:

4) no fare bucket availability for your location-of-sales

Something I totally did not have on my radar

It was clear to me that GPUs and mile upgrades track to R - but do paid upgrades track there as well (which was my question)?