In fact, one can say that there is no real reasons, like argue, to confirm the right clarification.

Clasification is a kind of scheme, which can better help people to understand or analysis something. That is to say that, it is only a tool. None of them can be absolutely correct. But, what is the better way to clasify? It depends one different people's understanding.

For the same reason, we have got our own way of clasification. So, we have got our results.