"in 2019, it passed laws limiting minors to less than 1.5 hours of online games on weekdays and three hours on weekends, with no game playing allowed between 10 p.m. to 8 a.m. It also limited how much minors could spend on virtual gaming items each month, with maximum amounts ranging from $28 to $57, depending on the age."

How could this be done without coordination?

In addition: "One of the first systems required by the government was launched in 2005 to regulate adolescents' Internet use, including limiting daily gaming time to 3 hours and requiring users' identification in online video games.[134] In 2007, an "Online Game Anti-Addiction System" was implemented for minors, restricting their use to 3 hours or less per day. " https://en.m.wikipedia.org/wiki/Video_games_in_China

Yes, coordination between apps would be the hard part and I see no evidence that it exists. There is a lot of writing in English that does not point to anything canonical from China. It does not make clear exactly what obligations are placed on app developers. I remain skeptical that coordination between applications is happening.

I would love to see any evidence of this. It should be easy if it exists as there would be documentation telling app developers how to use the central database. I would imagine an ecosystem of libraries would exist to make it easier for app developers to satisfy these obligations.