I agree that there are differences between a publication and a platform, but they are relatively subtle. And as long as the argument is "China through TikTok can influence which content is popular or allowed to be published at all", then that is leaning into the publisher-like aspects of TikTok, not the platform-like ones: and it is precisely these rights that are protected.

Just to give an example of what would be concerns of the platform aspect of TikTok, that would be concerns about the ability for the app to deploy malicious code to users' phones, or the amount of data that it siphons off legally. But those are de-emphasised in favor of their control on content, which is precisely what's supposed to be protected by the Constitution.