Actually your wrong. Alpha 3 states orignally controlled territories.
Major industrial complexes can only be built on originally controlled territories (this includes upgrading minor ones). Likewise they may not be upgraded when captured. Major industrial complexes are reduced to minor when captured. The original owner of the territory may upgrade it if the territory is recaptured.
I originally owned Shanhi/Kiangsu so as he Japanese I can build there. Maybe thats an Alpha 3 rule change that slipped through. It doesn’t say foreign countries.
Yes, Japan does start the game in control of Kiangsu, but it has a Chinese symbol printed on the map. That means that the original owner of that territory is China. The only territory outside of Japan that Japan can build a Major IC on is Korea because it is worth 3 IPCs and has a Japanese symbol actually printed on the map itself. I know this is kind of an oddball rule with Japan starting the game in control of Kiangsu, but you are supposed to pay attention to the symbol that is printed on the actual map to determine original ownership.
I disagree with that interpretation on the grounds that I understood the markers to mean that china could move into those territories which are chinese , but not orignally controlled by china at the beginning of the game. Original control to me is what territories you start with. NOT your interpretation of the rule. It sounds stupid to interpret it that way when original control clearly means what you start with is what you originally control.