I do see the change of shadow piano411 is referring to and I think he brings up some valid points in this thread.
Though I don’t have any personal feelings or beliefs about tuning pin twist so it’s impossible that I would get bothered about any perspective
If I had issues of tuning stability I’d be more concerned about the topic. I feel different things with the pin but I would not have described anything as a twist vs a turn. I seem to have a different lever technique than other tuners though, which I developed in response to working with an impact hammer.
I found UprightTooner’s video very interesting although I wouldn’t have found it totally conclusive. It seems to be missing information. For one, you can’t see the motion of the tuning hammer. It also doesn’t measure any other deforming forces (such as what piano411 has brought up). But I think the video is a great starting point.
Towards the beginning of the video, I readjusted the piece of pinblock in the vise. That may be where people see the shadow move. But what would the shadow moving mean? It means the pointer moved away or toward the card. This motion would not show as a change in the reading and is therefore insignificant.
But yes, I agree, more info would have been better. for instance, the pointer and card are positioned vertically from a point halfway between the becket hole and the pinblock so that IF there was side to side flagpoling, it would be on a neutral axis. (Think about it...) Also, I steadied the socket end of the tuning lever, which was really to make for a less jumpy demo, but would also mitigate any flagpoling. And of course since I was the one actually doing the demo, I had a feel for what was going on that cannot be conveyed in the demo. (I only explained part of this before because 411 was only interested in provoking, not understanding.) A simple answer to all of this is to try your own demo.
But as far as the residual twist, that is plainly shown in a before and comparison of where the pointer is:"Take note of the frames around 0:05 and 0:37, which are the pertinent before and after views. The first is before the tuning lever is applied to the pin, the later when it is removed for the 145 in/lb demo. For the 175 in/lb demo, the before and after views are 1:18 and 1:53."
Whatever is done with the tuning lever between these times is moot as far as the residual twist. The tuning pin developed and maintained a twist.