This sounds like a mangled explanation. It seems to me, somewhat naively, that the resonator must be held at a higher temperature than the rest of the circuit to produce work on the load.
I think some minuscule amount of energy is taken from the thermal bath (the environment is considered a thermal bath - you can take heat from it and it's so big its temperature won't budge), converted into electricity and then back to heat in the load resistor. They all remain in the same temperature if I'm not gravely mistaken.
