It doesn’t have to in terms of operating temperature. In order for the engine to operate at the set point of the thermostat then all you need is enough heat minus radiative and convection losses.So you think that 3 or 4 working cylinders produce same amount of heat as 6 do?
No manufacturer would ever want an engine to operate at less than the design temperature as that would be detrimental to efficiency (as well as other problems such as excessive oil deposits).