Interesting video. The wading belt appears to do more than I thought; I have never used one, since I always have on a drytop. I did wear a Home Depot style velcro back support (until I lost it), sort of like a wading belt on steroids.
Most people without a pfd would still be able to swim to shore at any part of pumphouse, but I think he just sank.
"Most people", but not all. People drown every year with no waders, no pfd. So the waders are not necessarily the culprit. I certainly agree that in bigger water, and colder water temps, a wader setup is going to be pushing it if you have any chance of swimming. On the other hand, at our local playpark or easy runs in the winter, waders+drytop performs like a drysuit as long as I stay in the boat.
I suppose that the implied comparison here is:
1. Whitewater-specific drytop + fishing waders.
2. Full drysuit.
3. Other options would be Whitewater-specific drytop + drypants or splashpants of some kind, designed for paddling. The paddling pants I have tried were not waterproof like fishing waders at all; although there may be better paddling pants with feet out there.
Many paddlers may go the route I did: start with leaky old paddling tops or a cheap splash jacket (designed for flatwater), learn that you need a drytop, better boat, neoprene cap, better gloves/mitts, then want to paddle in colder water. Since you already have a drytop, you are now comparing ~$100 waders, which have completely waterproof feet and available to try on everywhere, with a $600-$1000 drysuit, which may not be available to even try on locally. Around here we do not have much for big water runs, especially in the fall/winter. Using waders carefully served me well for a number of years. I swim-tested my setup in SWR drills, with not much water getting in, similar to the video.
Something else to remember; if a drysuit gets a puncture from a branch or something, it could fill up with water, similar to the wader concerns.
Another thought; now that I have a drysuit, I still wear the waders+ old drytop for river cleanup efforts. Keep your good drywear away from those russian olive thorn trees!