The Chinese side of this production puts the issue in a very different light. The problem in Hollywood for Asian actors is that they get very few opportunities and what opportunities there are have a tendency to go to white actors. Quite obviously this isn't a problem in Chinese cinema.
There, Chinese actors dominate the industry, filling at least 90% of the cast. And because the casts of this film industry is so uniform, there is a bit of a demand for foreign talent, and so it's not uncommon to see Korean and Japanese (and Hong Konger and Taiwanese) actors playing nominally Chinese characters. In a purely Chinese production this is a bit like a Hollywood film casting a black actor to play a character who would have nominally gone to a white actor. This particular film's heritage is a bit mixed, but it's still quite clear that the primary audience is meant to be in China.