I'm not a practitioner of Wim Hof's methods, but what was implemented in the paper is definitely not Wim Hof breathing.
The paper describes 30x breaths with the inhale twice as long as the exhale, and a 15 second hold on the final exhale.
Wim Hof's method has 30x equal-length inhales and exhales, and a one-minute hold on the final exhale [0].
Aside from there being a substantial difference between equal length inhales and exhales and an inhale that's twice as long as the exhale, the big idea behind Wim Hof's method is that that minute-long hold is very difficult, and trying to do it supposedly builds a certain kind of mental (really, holistic) discipline that a 15 second hold simply would not. 15 seconds is not hard unless you're pretty out of shape.
The Wim Hof method is weirdly effective. I've never been able to hold my breath for over a minute even though I've tried. But on my second attempt at the Wim Hof method I did 2 minutes and then shortly after 4 minutes... It felt way shorter... I think the hyperventilation put me into a dissociative state.
The paper describes 30x breaths with the inhale twice as long as the exhale, and a 15 second hold on the final exhale.
Wim Hof's method has 30x equal-length inhales and exhales, and a one-minute hold on the final exhale [0].
Aside from there being a substantial difference between equal length inhales and exhales and an inhale that's twice as long as the exhale, the big idea behind Wim Hof's method is that that minute-long hold is very difficult, and trying to do it supposedly builds a certain kind of mental (really, holistic) discipline that a 15 second hold simply would not. 15 seconds is not hard unless you're pretty out of shape.
[0] https://www.youtube.com/watch?v=tybOi4hjZFQ