There's a reason why they led with simply labeling author self-reported AI videos as AI, and then casually mentioned they'll also try to detect AI videos automatically. They're not confident in it working reliably and want people to have low expectations. This is probably realistic. Using AI to detect AI is not reliable. Detecting AI videos is likely to become an arms race and will require an ongoing commitment of resources.

This is better than nothing, but it's not going to provide immunity against AI fakes trending and having impact before they're identified as AI.