The policy states "content that contains links of usernames" will be subject to removal.

I think the "cross-posting" that the article is referring to is e.g. downloading a TikTok to reupload it to Twitter, or screenshotting Instagram or whatever. Elon can't risk LibsOfTikTok's entire account falling under violation.

I could be wrong about that interpretation of the policy though, because the wording is probably intentionally vague.