Doesn't the coolant thermostat control the engine temperature and not the running of the fan?
In other words, it is true that the fan will cool the coolant and lower the temperature IF the coolant thermosat opens when the engine temperature is up to the level that coolant can flow thru the engine and radiator. If the temperature is to low, then the coolant thermostat will close not permitting the coolant to flow or to restrict the flow to keep the temperature at a constant.
So it really doesn't matter if the side radiator fan is running all the time, the coolant thermostat controls the temperature of the engine.
The only reason that they have a fan clutch on a rear radiator diesel, is to save horsepower that is used when the fan is not needed, NOT because to keep the temperature of the engine up. It is also controlled by the coolant thermostat.
It is also the same on a front engine diesel or gas motorhome or vehicle of any type.