I could not find anything in the service manual to back your comments regarding type of transfer oil and transfers are leaving the factory with oil depending on transmission type and I know that from many years servicing Nissan trucks.
The deference between oils is just for one reason, for easy identification of oil leak In case of a leak between transfer case and gear case.
If someone wants to change oil type, although I would not recommend it, do a double change so old oil will not remain in the transfer case.
There is only 1 type of transmission in UK D22's, manual, therefore your statement re: different types is irrelevant.
The workshop manual clearly states both types of lubricant can be used, look harder.
Your claim of the only difference being to make it easier to identify a leak, are you having a laugh, I almost fell of my chair, rubbish!
I am certain Nissan never built any of their units expecting them to leak, so why make identification easy?
Lastly although you may, Nissan certainly don't recommend sticking with one oil.