How much of that narrative is due to pruning though. China has a long history of extreme censorship after all. One of the first emperor's most notable acts was, after all, the destruction of much of the hundred schools of thought. There is also the issue of splinter states later being declared rebels and killed off despite hundreds of years of autonomy, and the current push to wipe out non-Han cultures within the borders of China (RE: the opening of the Chinese Olympic games, and the anti-muslim concentration camps going on now).

Point being: how much of that trend is real, and how much of it is useful propaganda spread down through the ages.