Tony, thank you for all of those videos!!
I admit that I've camped less in colder weather in the last decade and a half than previous. That is mostly owing to health and preference. I did it in my twenties and loved it but in my forties, I can chose not to, lol!!
There are always tips and tricks to help with camping in extreme temps. In the middle of summer at our biggest reenactment, we have thousands of people crammed into a large open field where there is no shade. With the heat index, it can be over 100F on the worst of days. We use heavy fabrics under the roof canvas to help block the direct sun, which diminishes the temps in the tent by more than 10 degrees. We've done this in cold, as well, to help add an insulating factor and again, the difference can be noticeable. I know the Dyatlov group used "sheets" inside. I wish I knew more about those; when I first saw that, I was thinking of the thin cotton bed sheets but like many translations, I think they would be somewhat more substantial than that, else why bother bringing them?
I still do not think that camping on that very ridge in that spot was a good choice as so few people have ever actually done it in winter conditions.