You don't think the combo of sheer volume(=feedback) @92-98dB (see his meter), tons of gain and processing (AD/DA) could at least partially be the cause?
The dude is standing a few feet away from his cabs with a Strat (even with a humbucker bridge).
If I'm boosting my Engl Savage 60 on the lead channel at home, standing 4-5 feet (~1.2m to 1.5m) from the cab and I turn a humbucker equipped axe towards the 2x12 cab, chances are it will howl as well. Even at 85-90dB playing volume. And I don't have a fridge full of 80's gear tied up in between.