I don't know of any system capable of doing what you describe. But if such a system existed it could just use publicly available videos from Facebook and Instagram. It wouldn't need its own social media platform to feed it data.
Having a direct feed of videos being uploaded from the user's device is also advantageous as the higher resolution of the original video will provide more details before it is recomompressed for long term storage in a smaller resolution. Most importantly, Instagram and Twitter won't allow uncontrolled access to the content they host whereas a Chinese company simply does not have a choice and has to serve the content up on its state demands.
Until proven otherwise, it is safer to project that such a system exists.
I don't think China are going to find their Dissident in TikTok videos any time soon. The false positive rate on even the best facial recognition is way too high for tracking individuals globally.
Everything you've pointed to can be done already by mining the publicly available treasure trove of YouTube Shorts, Instagram Reels, etc. A pretty small team can scrape these sites and do what you're insinuating.
And lastly, I still don't see the danger of releasing this info? I mean, can't any foreigner travelling on a tourist visa record public vistas for 30 days and essentially do the same thing?
Facial recognition database and tracking people at a global scale.
With advances in computing power and unsupervised machine learning, correlating a person with the person's surroundings is now largely or fully automated – what used to take forensic experts weeks, months or years to hunt down a person by poring over indirect clues in photographs or CCTV camera footage, is now almost instantenous.
Remember, TikTok is not just topless teenagers twerking on the camera, it is used by people to take short videos at random locations (and the locations are already easify to classify and account for), so if you happen to be a dissident (or a person of interest in general) hiding from the CCP, and you happened to have walked past a TikTok user shooting a short video and you got in the shot, your identity is matched up and your current location is revealed automatically, in near real time or with a short delay.
I have almost no doubt that people in TikTok videos are already digitised, and their faceprints are sunk into a gigantic database behind the Great Firewall. It is easy to project what other kinds of nefarious abuse are possible when such datasets are available.