I don't think it's overblown. We've seen what can be done flooding social media networks with propaganda-troll accounts and memes. With TikTok China owns the platform, and TikTok knows what you like (see any number of threads with HNers shouting the praises of how addicting tiktok is). And, we already see China's influence in media. Games and movies censored or tailored to not offend China, so we know they're mindful about even subtle messages. I don't think it's unreasonable to be concerned about TikTok as a propaganda machine.