Basically the takeaway I got is that I (given my genetics) probably have good non-shivering thermogenesis, and I've run with this knowledge since then. I have worn a coat maybe a handful of times in the past five years. I wear a windbreaker to keep the windchill off my skin, but that's about it. I go curling in shorts and a tee-shirt.
The only thing that stops me from being one of those sadist ice-swimmers is that I have shit-ass swimming skills.