Dear lord - please don't associate me in anyway shape or form with him. John's very old school at heart but very up to date on technology and trying different things - he may not quite be leaning completely in some directions, but he is tilting. I need to ask him directly the exact whys of the deep air, he teaches it but not really in that sense - he's all about decreased CO2 with methods that include decreased WOB or He. My understanding of it is he shows you your limitations under a watchful eye, conditions, situations and expectations have an effect on gas selection, you have to take the next class for the actual He - I don't think in any way shape or form would he give you the approving nod on a 175' cold dark working dive on air, he probably wouldn't even at 150'.
I had an instructor that was disappointed I didn't take AN/Deco with him - he doesn't like Shearwater, he just got Multideco and while he may have dove deep a lot in the past, he doesn't today. Lots of old school knowledge though.
John jokes around a lot - it is a very fun boat ride but when he's making a point about something, the joking stops - tri mix 2 class final dive was deep, watching him and his demeanor during the class before the dive and the setting up on the boat, there's no joking around there, I think he said those dives scare the **** out of him if I remember right. Maybe back in the day but he just doesn't come off on those "got lucky hero" dives today - he's really quite the opposite - safety first, don't be afraid to GTFO - that hero **** is for barroom stories, not real life.