As with a lot of manufacturers, the Japanese stuff got too expensive so to remain competitive a lot of it moved to Korea, Taiwan and Phillippines, before taking the leap into China.
I've no idea how the quality of Japanese vs other in the AG range differs though so can't help you on that front. I've got a few Korean scopes from Nikko Silver Crowns, Gold Crowns, Bushnell and Apollo and they are all nice and bright. The few Japanese scopes I've had, have been just that bit brighter and clearer. Not much but you can see the difference.