I also thought the same, but the more I watch it, the less it feels like AI. The dangling thing in the handle doesn't change speed or disappear after she gets in front of it, and the speed changes accordingly when the treadmill lurches a little forward. I thought that her legs clipped through the thing dangling from the roof, but she actually just kind of hugs around it. The physics of her jump feel slightly weird but that could absolutely be just me overthinking.
The video is ridiculously grainy so it's hard to tell for sure whether it's AI or not, but that getup and the fact that she's doing that this casually towards fucking stairs makes me think that it's nevertheless an edit of sorts.
That's an interesting point. It does look that way to me if I concenrrate solely on the thteadmill, but if you look at her legs, you can see that the left one kicks the ground as she gets the momentum, which makes it go back looking plausible (at least to me) :(
But again, very hard to tell with the image this grainy.