Bent rear derailleur (RD-5701)?
I don't see any chain in the video.  It (most) will do that with no chain. The spring is (hopefully) strong enough to pull an untethered derailleur into the cassette.
Park Chain Length Sizing

Now the derailleur may also be bent but that is something different.

The rubbing in that video is only a problem if it rubs with the chain installed.