If my leaf is plugged in AND charging...then the heatpump (2014 SV version) and the heated seats and heated steering wheel work and run off wall power.
Example of the above: Turn Leaf off, plug into DC public charger, turn Leaf on. Leaf still charging, heatpump and such all operate from "wall" power. Or in this case the public DC charger. Love the fact that the car can be on, heated or cooled, radio on while charging for 20 minutes or so.
JJeff is right though. If plugged in and NOT charging, the heatpump and such are drawing from the battery. Active charging is necessary for heating to be drawing from wall power in my experience.
And to go further...if plugged in and charging at home or other AC charging points, heat is still drawing from wall power but only if enough juice is coming from that wall.
Example: my 20 amp EVSE upgrade can pull 240V X 20A = 4.8 kW from the wall. the heater "steals" at least 3 kW when fully engaged and cold. Only 1.8 kW left to go to battery charging. YMMV.