There's also just the fact that soldiers are often a bit crap at opsec it just doesn't always get them killed. I have doubts anyways that China would be feeding Russia strike targets based on tiktok usage anyways so they'd be stuck to using the videos to guide strikes based on the nation-state equivalent of GeoGuesser. That can be fantastically accurate but it's much slower generally.

What does tiktok offer in that respect that youtube or just about any other social media platform supporting video couldn't also provide?

It's something that GenZ actually uses that is run by a friendly state.

China is a “friendly state”?

relative to Russia, yeah? China isn't like, literally invading them. China could get ByteDance to pass location data to Russia, but it doesn't seem like China really wants to get in the middle of the war.