Reminds me of back when they claimed wine was good for your health
Turned out to be people affluent enough to drink wine regularly also had regular access to healthcare and were thus likelier to be healthy (for some definition of healthy)
Similarly here, I’m tempted to believe that anyone who does CWI regularly probably lives a healthier lifestyle in general and that CWI is just one element of a robust health routine.
It’d be pretty hard to tease out all this in a study like this. I think in situations like this the approach I’d take is:
See what the science says in terms of theoretical benefits, get some anecdotes from trusted sources, and when the stakes are low like this, give it a shot myself.
That said, noted that some of the other positives seemed to be a bit more directly measurable/observable, eg stress reduced after 12 hrs and things like that.