I think I will describe what he is doing slightly differently, maybe it makes sense to some and helps them, maybe it doesn't, it is what it is.
I would not say JJ does a front hand pivot.
I would say Jeremy has a very consistent Pre-Shot Routine (PSR). He lines up with the natural center ball shot line, and from there he drops his cue with a front hand offset (not pivot) and grip hand down the natural shot line (straight as he would say).
Over time, he knows exactly how to drop his bridge hand to compensates for swerve and deflection, and make the ball, at all speeds.
He has reduced front hand English and back hand English and all other factors to just one factor (FHE only). Using one variable instead of two or more is probably much better option for most players (more simple = better in my opinion).
I see this system as using one variable to compensate for English on your PSR, instead of multiple variables. 10,000 shots later, I'm sure he doesn't even think about it and struggles to describe it to us.