I think RESTRICT bill is fully in the interest of China to the point that it may have sponsored it covertly. It will basically change US into China 2.0 from the point of view of their citizens. It will crumble the facade freedoms that US was trying to put as an argument why two party system is any better than one party system.
Why would they when it validates their internet strategy? It just shows the CCP was 10 years ahead of the US when it comes to restricting what apps citizens can use (to "protect" them ofcourse).
If China benefits from TikTok then it's a fair question to ask if they are working to stop the ban of TikTok.
You're thinking short term. If the US bans tiktok, more countries will follow and american tech companies will have a hard time competing there. On these grounds chinese companies will be able to compete better because they're already used to running multiple versions of the same app targeted at different markets.
What benefits China more: tiktok, or turning US into oppressive state that jails people for accessing internet wrongly?