I understand why Youtube could be fined for COPPA violations, they collect data on all users, and some of them were kids. But this video asserts that the FTC could fine uploaders for mislabeling videos for kids. How? The uploaders aren't the ones collecting personal data, Youtube is. Are they considered accomplices or something?
The FTC has not been explicit about how their threat works, but it probably involves holding Youtube and channel-owners jointly liable. Already, Youtube has been held massively liable for child-directed content that they didn't create.
Under COPPA regulations, a
Web site or online service directed to children means a commercial Web site or online service, or portion thereof, that is targeted to children.
Hence a particular channel can be a "web site directed to children".
In general, when an action involving actions A and B is prohibited by law, it is not a defense for collaborators to say "I only did A, he only did B". In this case, Youtube and the channel owner may jointly define the "operator" (who collects information) and the "website" (which is directed at children). Regardless of how many people are involved in carrying out the prohibited act, it is the act that is prohibited, and subject to civil action as an "unfair or deceptive act or practice". However, it is too early to tell how or whether this will actually play out in court.