It’s not quite this simple. If we made the V5 Smart Motor housing out of metal housing, we’d actually have worse effective performance because of government safety regulations.
If you touch a very cold or very hot object, the speed at which you’ll get frost bite or burns is based upon how quickly the temperature of that object can transfer into your exposed skin. Since plastic is a worse conductor of heat than metal, safety regulations allow exposed plastic surfaces to reach a higher temperature than exposed metal surfaces.
If we made the V5 Smart Motor housing out of metal, the over-temperature condition that triggers the internal firmware in the V5 Smart Motor to throttle back motor output power would kick in WAY faster to avoid having the exterior temperature of the motor housing exceed safety limits.
By using a plastic housing, we can run the motor at peak output power longer before triggering the over-temperature curtailment, but at the trade-off that it will take longer for the motor to naturally cool down back to room temperature.