The Security Council is nothing more than the principle members of the Allies at the conclusion of World War 2. Communist China didn't replace the Nationalists on the Security Council until 22 years after Chiang Kai-shek was driven off the mainland onto Taiwan. Since Mao and his old guard were doing their damndest to replicate the starvation and political purging of the Soviet Union in the 20s, it probably didn't matter that much...