Your attention is focused on wrong quadrant . Look at 3rd one ( anti clockwise counted) - you have way higher reverse current for hot diode. At almost two orders of magnitude higher reverse voltage. Sure - this part of loss is not as high as losses in first quadrant but they are going blatantly in opposite direction. And keep in mind real doiodes have their conductive connectors too. So total loss is a sum of few components. And their ohmic loss increasing for sure along the temperature rise.Thermal energies make it easier to overcome the diode drop, and so increase efficiency.
voltage - Why does temperature modify the characteristics of a diode? - Electrical Engineering Stack Exchange
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So, a hot diode has higher efficiency.
Your blatantly stupid sentece was a wrong generalization for all hot semiconductors. You cant say the same about power mosfets for sure.
I'm too lazy to teaching you all rudiments here.