I don't know what percentage of the tortoises in China are WC. The ones that I have seen from various Asian countries where the people were asking me for help have all been CB. The people said they were, and they appeared to be to me from pictures.
How does it lead to death? emysbreederMixing species is a dangerous practice and often leads to the death of one or all of the participants for a variety of reasons. Someone either did this accidentally, which denotes irresponsibility on at least some level, or they did it on purpose, which is despicable in my opinion. While radiata might be more common in the trade now than ever, they are still and endangered species and if they are going to reproduce (which I think should be encouraged) they should be reproducing with their own species. For that matter, as common as they are in captivity, sulcatas are highly endangered in the wild too. Much more so than radiata in fact. Sulcatas are extinct in at least two countries of origin and likely a few more.
Because the harm is not obvious to you, does not mean it doesn't exist.
How does it lead to death? emysbreeder