As a heavy user of tiktok, most of these claims are anecdotal, and people just see what they want to see. Liziqi[0] has 18M subscribers on YouTube and seems to be far more effective of "soft propoganada" than anything I've seen on TikTok.
Twitter and Instagram Reels is far worse at surfacing destructive trends, it seems like a misstep for the CCP to try and push TikTok in this way when our own homemade companies are more than capable of doing it themselves. Between TikTok and IG, only one of them has a "STEM" feed; and it's unclear why its the CCP trying to push more US kids into STEM.