Auto,
You maybe onto something at a practical level. And you post a question,I cannot answer. The 'magic' effect is when the aperture is close enough to the eye. At that point you do not have to work to center the front bead in the hole to hit the aim point. The aperture is similar to using a 1x scope. At some distance, and I dont know how far, you want to keep the bead centered. That is line up 3 points, front, rear and target. The round hole may still be a significant help, without the effect. At the end of the day this rear hole sighting system is working for you and may help others.
I did some reading and there is a way to test. I dont plan to do this. Just for the sake of conversation I will toss this out there. On a target rifle, the shooter can line up the bulls eye. Then move his had side to side and the front bead will stay on the bull. That is the magic. The bead will be off center and yet the poi is he same. As some point, with the hole mounted at a greater distance moving the head from side to side (putting the bead off center) will change the point of aim.
That above head movement is the same method used to test for parallax when adjusting the Objective on a scope. In fact the above effect is parallax.
