I'm not sure if this kind of idea is typical for Japanese or not but anyway it seems too childish. I guess it is popular because stereotyping others makes it easier to "understand" them.
Once my teacher of biology told us that blood typing is like a religion. "Some people believe it, and others do not." It was when we studied the red corpuscle and antigen on it, so the blood typing seemed untrue. IF you could classify people into four types according to the blood type, there would never have been misunderstandings or arguments.