There is nothing representing the temperature. IE, to meet the definition of analog it would need something like a thermometer resistor where the resistance is used by some electronics to turn off the main heater.
The pressure provided by the bi-metalic strip is representing the temperature, and it's turning off the main heater by causing the unit to pop out.
The "signal" doesn't have to be voltage, it can be pressure or spacial position as well.
Did you read the article? The cigarette lighter represents data (pops out) based on measurement of a continuous variable (temperature)