I would be convinced if you can find a Chinese citizen, in China, posting about Pro Taiwan or Pro Hong Kong videos on TikTok.
Tiktok is blocked in China and can only be accessed using VPN. Of course there are still people who do that, but I'm not sure how I'm supposed to identify them and verify their nationality. So you'll have to remain unconvinced.
Edit: Actually, if you could find that kind of video on another platform, it would be possible to upload it on TikTok and see what happens.
That seems to be a meme on TikTok: https://www.tiktok.com/@smokingpineapple/video/6747343325621...
Edit: Also this hashtag: https://www.tiktok.com/tag/chinazi?lang=en Less than 4000 views implies that it might be censored, I guess?