This might be a dumb question to ask, but what exactly is this useful for? B-Roll for YouTube videos? I'm not sure why so much effort is being put into something like this when the applications are so limited.
To really do well on this task, the model basically has to understand physics, and human anatomy, and all sorts of cultural things. So you're forcing the model to learn all these things about the world, but it's relatively easy to train because you can just collect a lot of videos and show the model parts of them -- you know what the next frame is, but the model doesn't.
Along the way, this also creates a video generation model - but you can think of this as more of a nice side effect rather than the ultimate goal.