Right, it has always been a part of 2nd edition and the Alphas…
HOWEVER
The question was about Japan and UK. Now you have to be careful there. There IS a loophole that makes it possible to get around the exception, that is, it is possible to stick a UK destroyer in the Japanese fleet and prevent Japan from loading them in combat move EVEN THOUGH Japan and UK were not at war at the end of the UK turn.
This is possible if the UK does not declare war on Japan and then ANZAC DOES. Because their politics are married (UK/ANZAC) then Japan starts her turn at war with UK/ANZAC. The exception only applies if you declare war, initiating the at war status, but with the ANZAC declaration loophole, Japan was at war with UK/ANZ going into the turn, however since UK was not at war with Japan on UK turn, then UK was able to move a surface ship into the Japanese loading zone.
This IS a loophole and I believe against the spirit of the rules. If you don’t like it, I would suggest agreeing with your opponent that you can’t do a UK ship into Japan fleet followed by ANZAC DOW. But if you want to play by the rules as written, then this is a possibility and you’d better just leave some transports loaded at the end of J turn like Zhukov said