The 'Chinese' Theory: For and Against

[ololololo]

But he knew and understood the spoken language, by definition. Why did he not make and write down a translation himself? I bet it's much easier than devise an ex-novo tonal phonetic notation. And more useful too.

Knowing how the words are pronounced could have also had a lot of value. It would have been helpful for future expeditions or future travellers planning on communicating with people from that area, for one. 

There's also the possibility that the author also did exactly that (produced a plaintext translated version), but that it was lost or destroyed. Of course, we'll never know.

Is there a possibility that the author didn't fully understand what he was writing? So, he might not have known some words (which is possible for such a vast book), but he didn't explain them.