The issue isn't whether TikTok is currently doing it or no, its whether this is a national security risk in the future, which is absolutely is. I think he's an idiot and he's using the issue to distract from Russian interference, but its a concern that if you only wait to address this _after_ its already a problem, it will already be unaddressable for the reasons enumerated in my comment.

But it might have something to do with Facebook advertisement paid by whoever pays more.