Louie, I think Ken's fridge and yours are hybrid models. They retain the passive "cycle defrost" system with the exposed coil, but have the added feature of a heated defrost for the freezer section's coil, which I presume is hidden behind the rear liner.
The exposed coil in the refrigerated section is tied into the cold control. When control shuts off the compressor, it waits until the coil is a few degrees above freezing -- 37 or so -- before letting the compressor kick in again. This effectively allows the condensation to melt and run into the trough and channel its way down to the drip pan.
So, every time the fridge cycles off, the fridge section is defrosted.
The freezer, OTOH, only defrosts when the timer initiates the process (two or three times every 24 hours) and the timer overrides the cold control. If the compressor is running, the timer will shut it down. If it's not running, the timer will keep it from running until the defrost cycle is over. The timer initiates the heating process to melt the condensation off the freezer coil, and the whole operation takes about 20 minutes.