OTOH I don't have much confidence in the middle manager theory, either.
In foreign affairs, Beijing is sovereign - including anything related to the Senkaku / Diaoyu islands which are presently owned by Japan. So in this respect you are right.
For local matters, there is considerable flexibility and internal conflict. Currently, Beijing encourages citizens to find fault and report administrative issues at local levels, but will brook no dissent of its own management. In domestic administration China is less coherent than your claim.
All of the above could be equally true in a non-authoritarian form of government. I would argue that China's authoritarian politics are largely orthogonal to its degree of federation.
Your social credit score will go down if you do.
I am pretty sure China considers itself a "democracy" in the original meaning of the word: "rule of the people" (thus the focus on "People" in "People's Republic of China" and in many other official names). Basically, anyone can rise to power by going through the ranks of the communist party, and people are elected and voted for.
I wouldn't consider it a democracy even in that basic sense because of the disregard for basic human rights and freedoms, and it surely is not one in the modern political sense of multi-party systems.
Similarly, one could argue that the de-facto two-party system in the USA is not very democratic either, as it's not unlike a single-party system in China: you go through the ranks of the *party* to progress. It's the other things that make USA more of a democracy (freedom of speech and protections against unsubstantiated persecution, for example, and sure, ability to start a party too — even if it's inconsequential).
China has over a billion people. That one middle manager in the maps department is personally offended by territory appearing smaller, has zero relation to the rest of the country and shouldn't affect your opinion.
Many bureaucrats in the USA draw stupid lines in sand that nobody cares about, yet the USA is a strong superpower nonetheless.