It seems that they have been shifting more production there and relying less on Yanmar to build (nearly) complete tractors for them. I suspect that stems from Yanmar buying Cub Cadet and marketing their own tractor that is identical to the 2720 that they build for Deere. Although Deere will still use them as the source for engines, I think Deere doesn't want outright clones of their tractors competing in the North American market. I think Deere was happy with being the sole outlet in North America for Yanmar built tractors, until Yanmar changed that relationship.
My 2520 says "Yanmar Co Ltd, Osaka Japan" right under "John Deere" and the serial number.