Time Temperature
Mostly depends on if the timing system is somehow routed through the heating system, and or some sort of thermostat, IIRC. Our Kenmore/Frigidiare 18" model has a mechanical timer that has a specific on/off section as it moves round for heating. If one has not selected "water heat" the dw still will "sit" in that area for a particular time, then move on.
To me this means that the heating system is designed to heat by time not temp. That is if the water does not reach the desired temp within the alloted time, the dw does not "care" and will move on.
During the winter months when the boilers are on, hot water out of our kitchen tap reaches the 135F-140F or higher range, and the dw takes the exact amount of time to complete a wash cycle as during the warmer months with the boilers off and hot water only reaches 120F or a bit above.
My vintage Miele washing machine has the same system, that is the timer is not routed though any sort of thermostat, but uses an alloted pre-set time to heat water. Mind you on 220v power it will reach any of the selected temps, up to 200F quite quickly. However on 120V (this machine runs on both 120V and 220V, one has choose temps/cycles carefully and watch the timer. Thankfully can control incoming water temp from the taps and usually use warm water to fill when using temps of 140F and above, and sometimes even 120V as it speeds things along instead of starting from tap cold water.
L.