That's rather odd? The whole point of a dishwasher, I assume, is to save a lot of time and water, and then to get clean dishes. There's nothing unusual at all about spending a bit of time to learn how to use a tool to save time later, like learning an IDE or what have you. Of course, if you're already getting clean dishes then I suppose no further tool learning is needed for you.

My brother the dishwasher could use up 10x more water and 99% of people would still use it. Nobody buys a dishwasher to save water. That you position it like that gives me little confidence in the rest of the analysis.

That probably just means you’re using your machine badly.

There's no user error, just bad design.

This is an aphorism, not a truth. But it’s true that dish washing machines are often badly designed, especially when there are multiple opaque options that can be turned on and off. Consider the example presented in this very video, where the “Eco” cycle uses more water and more energy than the normal cycle and where the “High Temp” option adds more wash cycles as well as heating the water for longer. No amount of design can save the user from misunderstanding what these options do. The only way for the user to use the machine correctly is, at a minimum, to read and learn from the service guide (or other documentation) which gives explicit details about what each wash cycle is supposed to do. If you watch the supplementary video you’ll find that even that was incomplete and had errors; full understanding required hacking the dishwasher to reveal which parts of the machine were active (inlet, heater, pump, etc) and for how long.

Therefore I stand by my assertion that if you refuse to learn the details of what your dishwasher actually does then you will probably be using it badly.

I don't understand, though. You make the point that the user needs to read about the machine, but the very fact that the user needs to read about the machine points to bad design. A well-designed machine wouldn't have called a mode that user more energy and more water "eco".

I didn’t say that the machine was well designed. I said exactly the opposite! The very fact that it is not well designed means that you cannot rely on your intuition when operating the machine. If you do not have some idea of how the machine operates then you will operate it badly. In the specific case the video examines, operating it badly means blindly operating it in the default mode when a different mode demonstrably works better.

Oh, then we agree, we need to make up for bad design with lots of work (in learning how the machine works).

Right, and bad design is all around us every day. Learning about how your equipment works is a good idea!

I agree, but telling an overworked parent because their dishes are dirty because they didn't take the time to deeply understand the mechanism of their appliance doesn't tend to go down well.

If a machine doesn’t function correctly or well, then fixing it requires blaming some part of the system that can change for the better. The dishwasher cannot change; it’s just a machine. It could be replaced, but that might be expensive. Much cheaper for the operator to change what buttons they press on the dishwasher instead.

If that requires reading a manual, or carefully timing the actual length of each wash cycle, or making a recording of each of those wash cycles so that you can work out how long they fill for and how many pre-washes and rinses that they each do then so be it.