Well this guy in Antarctica has one at this very moment. https://www.colinobrady.com/theimpossiblefirst/
(If you hunt for it, there is a link to his Mapshare on that page...)
But that doesn't really answer your question. Or maybe it does, whats the temperature at the South Pole today?
I think I'd keep it in a pocket closer to your body heat at any rate. It might still get signal through a coat.
You can text without connect to the phone correct?
Yes, the "big" inReach (Explorer and Explorer SE) do not need the phone at all to do their job. When you pair the phone it makes it easier to type, but you can manually enter text with the buttons, somewhat slowly but not too bad.
Now there is a new inReach mini, which is a tiny little version and it relies on the phone more I believe. I think it will still perform some functions without it, like send preset messages, but not free text.
I don't like that the batteries are built into the devices. Wish they didn't do that. Nice to carry just a couple extra battery packs, and not worry about trying to recharge them.