Any mention of Wim Hof deserves a mention of the fact that the "Wim Hof Method" has a perfect verification mechanism: Wim Hof has a twin brother who does not practice the method and performs similarly well on most of the tests supposed to demonstrate the method's efficacy: https://news.ycombinator.com/item?id=24773331
From your link they checked exactly one thing: shivering response to cold following breathing exercises. Both twins did exactly as well on this one test. That's not "most tests". It's one test. And personally, being able to withstand cold is the least interesting claimed benefit of breathing techniques.
In other words: there's likely a genetic factor at play much like no amount of training will give you the genetic advantage Phelps has in terms of wing span and lung capacity: https://www.nationalgeographic.com/science/article/olympic-g...