It is complicated as in say put it this way: if a vietnamese girl one day bring back a chinese boy, or a black boy (not to say that there is anything wrong with either) to a typical parent living in rural areas and never exposed to anything outside the vietnamese culture region - can you say that the parent would not have the slightest apprehension about the whole affair, even if they do not exhibit the slightest discriminating actions.
There is no policy, official or non-official, people decides to segregate themselves, it is not something deliberate as in having some larger ulterior motives in mind.
Race-neutral as in equal right and treatment, But people's views of others is their own business.