If a Chinese composer composes, it is correct to assume that he will compose Chinese music, especially if he is a Chinese classical composer.
However, this score is fairly westernized. Most Asian music do not have themes, rather having an idea that is developed continously throughout a piece. Mr. Tan created static themes that fits too well in the Western notation. Also, not all of his ideas use the Chinese scales. This score should not be called "authentic."
What Mr. Tan did was to capture the tone of Chinese music and translate it into terms of western music. If the authenticity is measured by those terms, then certainly this score is more authentic then the frankly juvenile application of the Chinese scale by western film composers.
Also, for me, Chinese music is really easy to understand. I am not Chinese, I am Korean. Korean music has a more syncopated rhythm and a looser tuning system than Chinese music. Korean music is also more emotional and while Mr. Clemmensen objected to Mr. Ma's strained tone, in Korean music that would be a thing of beauty as the performer is expressing his inexpressable yearning. I enjoy and listen to Korean music, and after listening to Korean music, Chinese music sounds rather simple. And after listening to Chinese music this score sounds Western.