I've seen some of that, but mostly I see the joints move in opposite directions at all speeds. Many of the videos I've posted contain slow and fast sections. Occasionally I've even seen some MCP follow-through on pima block chords, but it's only for slow things, most guitarists are not following through at all into the palm from MCP. What interests me is what technique is required to play difficult things or to break through speed barriers, not necessarily to play like Paco, but to play the medium and fast passages required in the repertoire. For me, getting good tone and projection at slow tempos is the easy part, and you can get away with things that won't work at medium and fast tempos.
This is an interesting video because it appears like play-relax pendulum movements at slow speeds, but as she speeds up that movement is abandoned. I believe it's because the brain and fingers take over and do the movement that is required to get the job done. This is the crux of the problem, because what guitarists think they are doing is different than what we can see them doing. Her i finger does continue some of the pendulum movement but a and m completely change. Also, the releasing is a coordinated orbit not an instantaneous release as the play-relax technique would imply it is.