I just ordered a M3LR. My sales guy said there is no heated SW in the 3 or Y. He said "if you want a heated SW it's a $30K upgrade to the S or X". It would be great if he was wrong cuz I live in NE and it's freaking cold. Although gloves are cheap...
It is cold - no question... but that said, I was pleasantly surprised last winter at how warm the Model 3 cabin gets. Not just warm but to-the-touch warm. Unlike my ICE cars where, even if the heat were running at melt-yer-face temperatures, everything else in the car still felt like a block of stone.