Sigh ... Z5 sold via Mercari. It went quickly after I posted a long description of the Nikon policy about warranty transfers. Of course other sellers have been less than honest about the warranty cards they proudly included photos of. In a very polite, and direct way, I made that very clear!
The Z5 cost me little, as I traded in some lenses and got nice prices for them. Now with the ¥ I got for the Z5, the Z6ii I just ordered was only ¥120,000 on top.
The moral is that one shouldn’t buy the cheapest option (the Z5) just because it’s the cheapest. But of course you don’t learn that until you do it.