In a 1.17 test world that I created a few hours ago, I was playing around with the powdered snow. Whilst I was standing atop a tower of it with leather boots on, I happened to crouch and sank into the snow. The thing was, with the boots on even completely submerging myself in the snow didn't even start to freeze me. I thought the issue might be that I was in creative,  but even when I switched to survival nothing changed. The boots gave me infinite warmth.

I also tried to take off the boots after and not have the boots on, ect. but I froze. Nothing else gave me warmth. Odd...