I got a theory: Might be right, might be BS.
First off, what got me thinking about this: I was shooting in a midsized tournament. I had a shot on the money ball early in a set so no real pressure. The money ball was maybe sixteen or eighteen inches from the pocket, the cue ball not much further from the object ball. Every bit of the shot fit between the corner pocket and the side pocket on the opposite side of the table with room to swing my stick comfortably. Normally slap this ball in without a thought. I couldn't see the shot! Silly when the angle is just off straight in, but I needed to come off the shot. I came off the shot, twice! I finally decided hitting the ball just off center had to work, Stevie Wonder could make this damned shot. I missed.
Less than a month later I was watching an event. Money ball final game of the set, Efren missed that shot. A later match, same event and same shot but Bustamonte was the one that missed it. Maybe ten degrees off straight in or less, how the hell can you miss this shot?
I believe the reason may be partially mechanical. we all have a blind spot in our vision in each eye where the optic nerve connects to the eyeball. Our brain compensates and just like animals with their eyes way to the side of their head, we see things as complete even when it is impossible to see the complete image or object.
These slightly off angle shots might be right where our brains are creating a synthetic image. My theory and I'm sticking to it until I get a better one. At the very least I was in very good company as Efren was best in the world and Francisco top ten, maybe top five.
Interesting reading:
https://www.webmd.com/eye-health/eye-blind-spot#:~:text=The spot where your optic,That's your blind spot.
Hu