There was an official announcement in 2015 that arduino.cc was partnering with Seeed Studio for manufacturing and distribution in China and other Asian markets:
https://blog.arduino.cc/2015/06/20/arduino-and-seeedstudio-announce-partnership/
The idea was that Arduino would have specific manufacturers for each geographic area, just as they had Adafruit doing manufacturing in the US. I don't think the intent was for the locally manufactured boards to be distributed outside their geographic territory, so you would get a Seeed Studio manufactured board if you bought an Arduino in China but an Adafruit manufactured board if you bought one in the US. I'm not sure what has happened since then. The manufacturing plan could have changed since the .cc/.org dispute was resolved.
Of course arduino.cc would likely not have arduino.org.cn on their boards (though I think they do own that domain now) but it could have been a similar agreement made between arduino.org and a Chinese manufacturer.