Is that the savings for Tesla's setup specifically (heatpump+octovalve)?
Well, others have COP 2 heat pumps in the cars - the large heat pumps you see by the houses in Nordics that can reach COP 5+ are massive size wise and they don't fit in any car. Car heat pumps have to be tiny. So, if tesla does super duper job, they could be looking into COP 2.5 heat pump. With that you would save 6kWh per each 4h of driving. Good result, but not THAT magical.