Yeah. Yanmar-USA does everything they can to discourage gray-market imports.
But the gray Yanmar industry in the US is booming, running parallel but separate alongside Yanmar's own support for the far lesser number of tractors Yanmar sold through their US dealers long ago.
When I went looking to put a ROPS on my US version Yanmar, Yanmar-USA said they hadn't ordered any from the fabricator for 20+ years. Long gone.
But Fredricks, a large gray importer, recently went to the same OSHA-certified fabricator in Minnesota(?) that Yanmar had used and had them produce ROPS for most (all?) of the gray models that Fredricks imports.
I now have a ROPS that has an OSHA tag certifying it for the Japan-market twin of my tractor, but they can't add my model number on that tag because I didn't obtain it through Yanmar-USA. The gray channel support is better than that provided by the original importer, and in this case the part comes from the exact same factory.
For service parts like the water pump, muffler, fuel tank etc, there are under $100 replica parts, probably made in China, that seem to be as good as stuff that comes from NAPA. Likewise the stuff you need for a major overhaul is available, but it will likely be shipped cross country from one of the half-dozen major support sites. These things are like old Mustangs or Jeeps, the parts will be out there for years.
The gray Yanmars are well supported, just not by Yanmar-USA.
The legal situation for the Kubota trademark is different. I don't understand what the difference is, but Kubota has a court order telling Customs to refuse landing any gray Kubota. Canada isn't bound by this order, gray Kubotas are legal there. I think any gray Kubota you might find in the US is near-unsupportable.