Yes I also have flocked brushes. The problem I have with them is the rinse - what happens is I rinse quickly and close to the glass. Sometimes unknown to me the flocked bristles might just trail on the glass without me feeling it or knowing it's happened. I end up with an odd trail of spots going horizontally where I've zig zagged or moved on to the next window. That's why I stopped using them.
I inspect a lot of my windows very closely when I've finished - you'd be surprised at how much dirt isn't taken off and how many spots remain.
Since the storms none of my customers windows are cleaning well enough for my standards with any brush. I certainly wouldn't be happy with the results cleaning like the second vid at the moment. I've had two complaints in seven years, one was a conservatory roof where the algae from the finials washed down the first side cleaned and the other was for smears (impossible). I'm really particular and have never produced perfection yet.
In fact cleaning windows really gets me down because I don't consider the results good enough with wfp. Trad I've never mastered either to the point where the glass is perfect in low sun. Bugs the hell out of me.