take a look at the dna charts they have. people in guangzhou are half or more southeast asian by descent. the admixture goes up to 20% even in the north because in the past the southern provinces were full of poor people that couldn't farm properly and got distributed to the north as slave labor
the chinese themselves say shanghai is firmly in "the south". and look, it's solidly in the middle of the country. the south existed as a gigantic slave plantation for a thousand years. the chinese have been in taiwan for less long than canadians and americans have been in the new world.