I don't read "software backdoor" from that article; the idea that the software is susceptible to cyberattacks and the idea that it comes from China are two different things imo.
I've said it before: the TikTok ban reeks of "China bad" jingoism; we're concerned about yet-to-be-proven, hypothetical security risks because the software is built by our biggest economic competitor, not because it's provably dangerous software. Any justification for restrictions or regulations can be applied to the social media and technology space at large. Restrictions and regulations which I'm in support of, by the way: facebook and twitter have had a deleterious effect on political discourse and the movement/manipulation of information, and could be easily pointed to when it comes to the rise of MAGA, the Proud Boys, and other more immediate threats to American democracy.