And of course they'll be setups that use solar heating or are programmed to heat by time of day.
This is all down in the weeds though because a dishwasher does not use very much water.
i also went to american lg website and checked manual of cheapest dishwasher that they have. it doesn't instruct to run water either. it says that if water is not hot enough cycle will run longer.
anticipating comments that LG is not american enough, i went to GE and checked manual of cheapest (349) dishwasher. it doesn't instruct to run tap either. it does say just like LG that if water not hot enough, cycles that use hot water will take more time (because water needs to be heated)
as a concrete example, the video has a section in it where he shows that his doesn't so any sensing - hot or cold water have exactly the same timing on the heater's use (and resulting water temperature graphs).
so like. I agree with you that it should be true, it's simple and cheap to implement and it obviously works better. unfortunately it's not a sane reality for tens (hundreds?) of millions of people.
cheapest GE dishwasher that i found now - $349 heats water. of course, for video he could go and find some ancient dishwasher that doesn't heat water just to make a point (or maybe he has a broken one ? ), but i think it will be outlier today.
