Thanks guys. I'm really bad at refrigeration theory but the warm air rising thing is something I can understand.
Within the first half hour of the freezer running after being defrosted, the coil on the ceiling was the only one that had developed frost, and that coil had no ice on it at all prior to defrosting. I presume this situation is due to the Red-E-Defrost generating heat that rose and warmed up the ceiling. Once the defrosting was over, those two previously frozen-over coil shelves were cooler than the ceiling coil, I'm guessing.
I was told long ago that on an old school evaporator in a single-door refrigerator, when a pot of boiling hot water was placed on the evaporator, it would "recharge" the compressor. I know this practice has some type of effect, because it always generates the sound of circulating refrigerant, but I don't know if "recharging" is the right term. Whatever effect it had, it never seemed to be a lasting one. I've also been told that with an old school evaporator freezer compartment, using hot water in the ice trays would result in ice cubes faster than if cold water was used, when the trays are metal and placed on the evaporator surface. So maybe the hot water gives things a charge, but not necessarily a re-charge?