If this performed an essential function, it might be useful. But my own experience is, and this is echoed by many is that at full brightness the instrument lights are not very bright to begin with. Not certain why, in the face of an easy bypass, why one would be varying the brightness from nothing to not very bright, and pay a lot of money to do so...
I don't know if the terms are 100% interchangeable, but from my early days working with electrical systems and electronics, a variable resistor that was wirewound was called a rheostat, and typically used for higher wattage applications. A semiconductor version using carbon or cermet or similar was called a potentiometer.