Have never thought of it as AF. I have issues with understanding the concept of AF anyway.
I had completely disregarded the AF part of the official back to 20/20 course, got back to no corrections and then joined the forum. And that was the first time when I met this “obsession” over AF how / when /is it AF / how much, etc. I’m still puzzled over this part to be honest.
The brock string is more a thing of convergence / divergence for me, how the eyes are a bit further apart when looking at the distance than they are when looking at something close up. (The ~2mm difference in PD in bifocal glasses.) And sometimes I get / got this PD change incorrect resulting in DV or ghosting. (Note: I don’t wear glasses to guide me to the “right PD”, I have always been uncorrected or with contacts)
That was something I had to relearn that the eyes widen or narrow just to the point I need them to, not more not less.
The convergence divergence exercises in vision training are all about merging images or splitting them. This is what happens with the brock string for me. Beads become one and string becomes an X, or strings become one and beads have ghosts. With the brock string I can’t keep the strings’ last bit and the meeting point and the beads all clear and sharp at the same time.
I thought that was normal but can live with it if it is not