Why the Four-Power Treaty used English and French

Why did the Four-Power Treaty not retain an authoritative Japanese-language copy?

Japan was content to use the English text, while France insisted that the treaty also exist in French.

The Japanese delegation accepted English as sufficient and preferred the simplicity of one working language. France required a French text as well. The final English-and-French form therefore records which delegation pressed the language issue. The absence of an authoritative Japanese copy does not indicate Japan's exclusion from the agreement.