There has been a centralized bureaucratic autocracy in china since the legalist reforms of qin, a couple thousand years ago. Yes, the empire once united must divide but even during the long disunity before the sui and tang, there were multiple centralized autocratic states. Unity across all of the territory called modern china is not necessary to have a centralized state.

forcibly “united” by external forces, such as the Western powers in the 19th century, dividing up and ruthlessly controlling economic spheres of influence

Wait were western powers dividing or uniting china? You're claiming both in the same sentence. But that's kind of immaterial to my point that the centralized autocratic state has existed in china for a couple thousand years and that many important new technologies came out of the cultures governed in that way.