Leo, glad to know it's not just my machine doing this. I hadn't even noticed that you can sneak a reload of fuel into this ( which buys you an entire day of time )
Personally, I like the fact that Japan can somehow manage to carry not only the troop, but also drop them off with supplies ( which exceed the capacity of the ships

).
I have yet to manage to pull this off with the Allied ships, just can't manage to find the *right* combination of ships to make it happen, but due to the size of most Allied units, it is tough putting together enough ships to do this stunt early in the game.
If I manage to pull it off with Allied troops, I'll post exactly how, because it will even out the *exploit* factor if both sides have the same option. What I find strange is that it has yet to work for the Allies. I would presume that this is generic code in use by this routine, not customized based on the side involved.