I also have that sticker, and when I investigated with my dealer we came to ther conclusion that the added weight of the rear entertainment system - which was added AFTER the vehicle came off the assembly line in Japan - was the reason behind it. It was our understanding that the standard door label listing GVWR, etc. covers all items on the vehicle at time of manufacture. The rear entertainment system, apparently, is not installed at the time of manufacture and therefore must be covered with the separate sticker.
HTH