China has indeed blocked tiktok, but their version, douyin likely runs on similar systems and have similar types of contents. These two versions just don't share content and probably have different moderation and privacy policies.

I think you are confusing the tiktok block with the computer game ban, which requires excessive verifications (even biometric) to play games. And underaged children can only play games in assigned time slots with time limit:

In 2019, the country imposed a cybercurfew barring those under 18 from playing games between 10 p.m. and 8 a.m.

Recognizing that wily teenagers might try to use their parents’ devices or identities to circumvent the restrictions, the Chinese internet conglomerate Tencent said this week that it would close the loophole by deploying facial recognition technology in its video games.

https://www.nytimes.com/2021/07/08/business/video-game-facial-recognition-tencent.html