As an instructional video it's not so hot. He keeps advising short and jabby strokes as if that were key to getting the action you want. That's kind of a red flag. And he elevates more than necessary and doesn't have a very textbook stance and bridge.
All that being said, he's not necessarily wrong. With a very level cue, and perfect accuracy... a low left shot goes straight back the way a low-center shot would. But when you elevate the cue a bit, it really does send the ball back 'diagonal' a bit. We all have a hair of elevation, and you can have more... either intentionally or accidentally (like this guy in the video).
I remember john schmidt having to do a shot in a 9b match (forget the situation, it's on one of the bclub youtube videos) where he was too straight on a ball and had to get the CB to travel quite a bit, and used the little-known elevation trick to eke out just enough extra angle on his draw shot. The commentator knew exactly what he was seeing and explained it, and that's how I learned about it.
PS: in this case it's nothing to do with deflection or swerve. If the ball deflects it would go back at an angle opposite to the english you used. The ball's not curving in a quick mini-masse because the shot is sliding a very short distance and is being struck quite fast/hard. There's no time for it to curve.
Good post by slh. I think this is one of those subtle pool things that more people should know.
ok thanks for the post. I was sure of this but this video confused me.