While it does not seem enough to guarantee authenticity, this scheme does seem like it would prevent creating a video from scratch pretending to be taken at a protected location without having express knowledge of the key or the flickering at that moment in time.
Definitely interesting for critical event and locations, but quite niche.
It's similar to any other private/public key scheme: it just serves to prove the signature was generated by the owner (here whoever owns the location at which the video is taken).
But I guess you could imagine multiple flickering patterns per location, with each pattern being owned by a different entity (an NGO + a governement + a private company for example), in essence doing a multi-sig of the video.
Definitely interesting for critical event and locations, but quite niche.