Thank you, Keith. Sounds more like a franchise policy than a dependence of a Japanese venture
Keep in mind that not every country has the same laws governing warranties and the sale of goods, including different taxes, and consumer protection laws. It costs manufacturers real money to comply with these laws, warranty work itself costs money, and if that cost isn't built into the sale price of items, then the official servicing facility loses money. Every "baby" Nikon, Nikon USA, Nikon Canada, etc, has to stand on it's own, and they operate independently. This comes down to how far each "baby" Nikon is willing to go in the name of customer service, or perhaps more appropriately how much it will cost them.
The grey market phenomenon isn't restricted to photo gear, and it certainly is not restricted to the USA. You say it's important to you to support Nikon, but you, like most of us, look to buy your Nikon gear at the best price you can get. That might not support the "baby" Nikon where you live, even though it supports the manufacturer, Nikon Japan.
We can buy grey market Nikon gear all day long here in the US, it's perfectly legal, but it is not warrantied, or subject to service, by Nikon USA. Yes, you can send it to Japan for service under Niko's International warranty, and good luck with that if you don't speak the language. Sellers (B&H, Adorama, etc) can offer their own warranty on grey market goods, but how effective that might be with modern high tech gear that Nikon will not sell parts for to third party service facilities, is an open question. One might expect extended delays in getting the items serviced under those conditions. Not only will Nikon USA not sell parts or technical info for this gear, they won't train non-Nikon people to use the special equipment needed to do the work.
Some grey market items differ from official imports because they were made to comply with different laws and/or marketing situations. Cars are a very good example of this, and all cars registered in the US have to meet US safety standards that might not apply to the region that the cars were originally intended for.