Playing as the Americans, I thought I had made a mistake when I accepted Arabia as a vassal--the oil I took from them didn't seem to count towards the UHV. Eventually I cancelled my deals with them, and suddenly the oil did count, and I won the game. So oil resources count when controlled by vassals, but not when they trade it to you. What is the intended behavior here?
(I can provide a save on request)
(I can provide a save on request)