It's partly a Wim-Hof thing, I've also read other things which talk about the benefits of cold showers.
As for cold showers' effects on adaptation, tbh I've suspected that at various points in the past when I've compared my gains during periods when I do or don't have a cold shower post-workout. Anecdotally I've felt that I adapted better during the periods when I either had a hot shower post workout or didn't have one immediately.
This makes some sense too as a lot of professional athletes advocate the recovery boosting benefits (as in they decrease the time you need to spend recovering) but to me this sounds like it would 1. Shorten your anabolic window 2. As localised muscular inflammation is required for you to make gains, as cold showers reduce muscular inflammation, they would therefore hamper a requisite of muscular adaptation which should mean that your potential for adaptation is reduced
I'm going to mix things up a bit to see what happens