Is it still possible to plumb hot water into such dishwashers? Then the heating element have less work...
I bet some manufacturers don't even use temperature sensors in many models, and just assume an approximate incoming water temperature, and heat for a fixed time period according to calculations on amount of water in the system. This guess comes from the impression that cheap temperature sensing circuitry isn't the most reliable long-term.
I bet you're wrong. Is there a website where we can make an adjudicated bet JUST against each other. How many dishwashers come without a hot-wash option? Any dishwasher that didn't heat water enough would struggle with hard fats.
My dishwasher has a scalding 75°C option.
How did you conclude that they aren't the most reliable long-term?
Temperature sensing is extremely simple and cheap. Bi-metal contacts have been used since the dawn of electronics, and the solid state versions are also really simple. (Making components that are temperature invariant is the hard task.)