I've been doing some googling on autophoretic coating, using keywords like 'issue', 'performance', 'problems', and 'corrosion', and the only hit implying there's a problem is that University of Michigan report.
I'm not a particular fan of galvanising chassis, it seems to me that the Morgan chassis needs a coating which is not inherently brittle.
Still, I expect it's an issue which actually isn't going to impact on many owners. My original 1986 chassis was simply painted, the car had a very hard life before I got it, and even so the chassis lasted well over 25 years before it needed replacement.
I see no reason why an autophoretic-coated chassis, properly looked after, wouldn't easily outlast this - and to be honest that's probably much longer than most owners will keep their cars.