I do have seat heater controls on my app 3.8. They seem to default to setting 2 but can be adjusted from 0 to 3 individually. The seat heater icons are right below the heater flow arrows. When I checked to see if they were on, the seats felt cool to the touch but when I sat in one and adjusted it via the app, the heater was on (however, as soon as the door opens, the climate control turns off — use the app to turn it back on again for experimentation). Try adjusting the heater in the seat you want to 3 on the app and see what you think. You need to be running app 3.8 or higher for seat heater controls.
The V9 thread for classic cars is here:
Software Version 9 for Non-AP/Classic Cars