I dunno. I buy it at a very granular level, but the problem with most things that purport to be fat loss boosters is that your body and metabolism adapt.
Like, cardio burns calories but it's not really an amazing long term weight loss strategy at all because human metabolisms adapt. There are hunter-gatherer tribes where people go 40,000 steps a day.
So yeah thermogenesis, burning calories, it makes sense but I bet people get hungrier or whatever after being in cold water for 2 hours.
We should ask Ohtani about it at the press conference