Is it that hard to understand? Twitter and Facebook will at least try to make a genuine effort to root out and ban "coordinated inauthentic activity" by the Chinese government (and if they don't they could probably be compelled to do so): https://www.theguardian.com/technology/2020/sep/23/facebook-.... A Chinese-owned TikTok won't: either it won't do it at all, or it will make a fake/bad-faith effort.
Similarly, Twitter and Facebook may gather a lot of non-public user data, but there's pretty much no chance that any of that data will be willingly handed over to Chinese intelligence.
It should be noted that Chinese intelligence is not exclusively after top secret government data: they're also interested in many kinds of mundane information that you might be surprised by that can be leveraged to get it: https://www.nytimes.com/2018/12/11/us/politics/trump-china-t....