Actually, there are many options for waterproof insulated outerwear. The mystery is he chose the one that was not waterproof. Also I don't under stand the claim that he was cold in the Glitchin'. I checked reviews for it from different retailers online and I only found one review that complained about it not being warm enough. Strangely that review was also from NY. I would not be surprised if the author wrote that review.
So why did the jacket that completely failed one of your criteria, waterproofness, win? As you acknowledge yourself, once down gets wet you're screwed.
Interesting, usually folks think of compressibility as a plus. You can make the item smaller so it takes up less room in your pack. Also a higher number fill bag of the same temperature will weigh less than a lower number fill bag, another plus.