Seems to me it's only guilty of the same data scraping for marketing purposes that Meta is... maybe even less so as I always found TikToks advertising less gross than Instagrams.
Both suck but TikTok is slightly less suck.
Is it really a security thing or is it a "We are getting pressure from US companies to remove competition" thing?
It's so much not a security threat that its board was (probably is now as well but the investigation is years old) to be full of former NATO shills: https://www.mintpressnews.com/nato-tiktok-pipeline-why-tiktok-employing-national-security-agents/280336/