Be careful not to confuse engine coolant temperature and electrical coolant temperatures.
For the heat engine the ideal world is to run it hotter, materials and lubricants permitting. The benefit is less energy loss and less cooling surface required. Ideally. So Mercedes has moved towards this, even designing the aero and suspension for hot tracks.
Again, and crucially the design and materials /fuels/ lubricants must permit this higher temperature running. I am not saying there is more waste heat either.
Electrical components are the opposite. You want to run them at cool temperature. Not cold, but cool. Hotter temperstures reduces current carrying capicty, magnetic fluxes reduce with higher temps. Insulation breaks down etc.
Not driving a Mercedes? Work harder!