POST-ACTIVATION POTENTIATION

I've never really tried out a PAP-style protocol. I've used some bastardised versions, like band speed squats after heavy squats that might be seen to fit into that. From a purely anecdotal aspect the idea of heavy loading before using lighter stuff has really been around for at least over half a century in some forms. Pre-loading & doing partials or negatives or even lock-outs to make a weight 'seem light' has been used in some form since at least then, this is a kind of formalisation of that effect into a training philosophy.
When you look for research on PAP itself, there's not that much in the way of research to back it up, not like many other protocols that are out there.
The main aspects seem to be:

1/ You need to be a good condition athlete to benefit
2/ The muscle (or muscles) in question need to be a high % of fast twitch muscle fibre (although some research has suggested that possibly endurance athletes benefit from this effect there is much less evidence for this)
3/ The effect is a direct one on the muscle used, so you must train the same muscle group involved in both activities.
4/ You must rest at least 5 minutes between the first & second exercise (an especially hard one for our man John!) as otherwise fatigue will affect performance
5/The rumour Ben Johnson did a heavy 600 pound squat minutes before his world record sprint is false (it's a common rumour, Charlie Francis, his trainer, squashed that rumour )

Bear in mind this is an unproven training device. & like many training protocols I suspect it may work for some guys, but not for others. I'd imagine an Olympic lifter might want to consider something like this as you could heavy squat, deadlift or even a hang high pull, then do a much lighter snatch or clean. That might be an experiment worth doing if you were a O-lifter.
Even if people have got good results, that doesn't mean you'll get good results, so start cautiously & see how you get on.
Sorry I couldn't offer more on this one.