If you use the paddles often if you tap and not hold you will change the settingMy experience has been the car will keep winter mode active (if selected) without regard to the temperature.
I will add however that I have experienced ( on my 19 model) the regen levels/mode settings have a mind of their own on occasion and resort to a different level then what I selected, so anything similar wouldn't surprise me.
Oh, OK, I don't use BlueLink for that. I do it in the car. Most of the time, I just leave them both at 100%, although never charge all the way to that.It is a known bug when using the BLUELINK app to change the "Target State of Charge". As soon as you use that function, winter mode turns off.