https://www.instagram.com/reel/DO9MwTHCoR_/?igsh=MTZybml2NDB...
The screenshots/videos of them doing it are pretty wild, and insane they are editing creators' uploads without consent!
To me, this clearly looks like a case of a very high compression ratio with the motion blocks swimming around on screen. They might have some detail enhancement in the loop to try to overcome the blockiness which, in this case, results in the swimming effect.
It's strange to see these claims being taken at face value on a technical forum. It should be a dead giveaway that this is a compression issue because the entire video is obviously highly compressed and lacking detail.