Interesting point about the Jerven bag there, John. But my thought is that they
should know about the latest (although they've been around for what - 20 years?) and proven effective technology? Otherwise its like saying a club is the best tool to take with you, because they hadn't heard of a knife
If you are teaching survival techniques to people going into hazardous conditions, is it not incumbent upon you to provide the best advice, rather than relying on century-old traditions? Sure, as long as you make it clear that - if you go out inadequately prepared, then a snow-hole might just save your life - or just teach it for the fun of people learning old techniques - fair enough. But I'm betting that every winter survival course teaches about the best clothing available, importance of layering, use of wicking materials next to the skin, importance of removing layering to avoid sweat, taking care of feet, appropriate boot/liners and importance of having spares and so on. So why not include a piece of survival equipment which in its simplest form weighs only 600 grams and is arguably much more effective?