I have a basis of knowledge about how language proficiency is defined (the federal government in the United States has a standard rating scale of foreign language proficiency, as do most other countries with an active diplomatic corps and military alliances with other countries) and I know how much time it takes in specialized training programs and in-country to become proficient in Chinese, none of which Snowden has. I would find it more believable that he has some knowledge of Japanese, because Snowden lived in Japan for a while, but he apparently has little knowledge of that language either.