Below is the full text of the San Francisco Treaty, and no where does it say that Spratly & Paracel island belongs to Vietnam.
San Francisco Peace Treaty
As China was not present in the San Francisco Treaty, it has signed a separate treaty with Japan, namely the Treaty of Taipei where Taiwan & Penghu are returned to China. The Spartly & Paracel islands are actually referenced in the treaty.
Vietnam joined in the conference.
Attending countries:
Argentina, Australia, Belgium, Bolivia, Brazil, Cambodia, Canada, Chile, Colombia, Costa Rica, Cuba, Czechoslovakia, Dominican Republic, Ecuador,Egypt, El Salvador, Ethiopia, France, Greece, Guatemala, Haiti, Honduras, Indonesia, Iran, Iraq, Japan, Laos, Lebanon, Liberia, Luxembourg, Mexico, the Netherlands, New Zealand, Nicaragua, Norway, Pakistan, Panama, Paraguay, Peru, the Philippines, Poland, Saudi Arabia, the Soviet Union, Sri Lanka, South Africa, Syria, Turkey, the United Kingdom, the United States, Uruguay, Venezuela, and Vietnam attended the Conference.
The Islands of Vietnam was in discussion related to righst of Japan after WW II. any case, the voting is the refute claim of ROC about " eleven - dash " 1947.