My wifehas a 2016 Escape SE Ecoboost AWD with Dual-Climate control that I occasionally drive. I'd never noticed this behavior until the bad cold snapthis Xmas. To me, it seems the area under the dash (floor AND legs) doesn't get the heat I'd expect. As you noted, heat from the defroster seems plentiful. If I have the heat up to hottest temp ("Hi") & fan at highest speed (7?) on 'defrost', I'll have to turn it all down after 10 minutes. From the waist up, I'd get pretty warm. If I have the same settings (Hi/7) on 'floor', it could run for as long as I've driven the SUV, and it didn't bother me on very cold days/nights.