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.)
If true, that is a recipe for a lawsuit if it went wrong.