This interpretation of the Chinese constitution is nearly 40 years old, companies comply with it, what do you expect?

Despite have a free speech clause, it also has a national security clause that is used to control all facets of life and override all other rights in the constitution. Anything deemed to slightly alter China/the Party’s unity is reprimanded and illegal. Multi party states can fall into the same trapping if they give their national security law constitutional force, always one court ruling away.

Yes, China is a single party system making the constitution redundant and any nominally marxist regime would find a way to do the same out of necessity.

Follow your Chinese AI in thinking mode to watch its opinion of Tianamen Square references, it will be candid enough for your sensibilities and show how it operates around guardrails