Well to be fair Kingpole says to work your way slowly up from the base to the frenulum, that's what gets you to the PONR.
For me edging is very different to masturbation, masturbation is purely going for climax/ejaculation in esentially as little time as possible with a palm's full grip that is more tight/rough than with edging.
Edging gives you the chance to be more exploratory and give slower, more gentle strokes to different areas, finding your own trigger areas, which eventually leads to ballooning.
As for your question about losing your erection when you reach the PONR and stop, that loss should become less and less with practice, from a 10 to 6 to a 10 to 9 or better. One technique to improve that is when approaching the PONR is to avoid the corona and frenulum and stay near the base, for around 15 seconds before the point of orgasm and for a while after. Howver this technique may not be appropriate when applied to sex so 'more realistic' practice may be better. Good luck.