That book is not generally accepted as factual.
I read the book a few years 6 or so years ago, so forgive me if I get some of this wrong.
The non factual parts of the story (as I have read) are the parts that discuss voyages beyond Africa. I’ve not seen (that I can think of) anything disputing that the Chinese got to Africa.
Just my recollection, so I will eat the words if I’ve misremembered.