Restaurants cycle dishes a lot during a single mealtime. Homes don’t. I don’t think “I can’t wait 2 hours” is typically a real problem.
The hot water is recirculated during the wash, the rinse uses fresh water from the tap with the excess going out an overflow. A little sump water gets replaced every cycle, but enough stays that it's back up to temperature before you've emptied and refilled it. There's also a small peristaltic pump to top up the detergent directly from the bottle.
Not much benefit in a home setting unless you fancy having it hot and ready 24/7 though.
This is probably the one trick consumer dishwashers should emulate
the task is prepare food, eat, clean. when you leave the kitchen and come back the next day the task is now different, its unpack, prepare,eat,clean.
you are constantly not finishing today's tasks. it lives to see another day. if you can fix it, bound it to the workflow, you will be a billionaire
Because they need space, they need even more nasty chemicals than domestic dishwashers, they need a stack of trays to load the dishes on and a crew to load and unload them.
If you want a dishwasher which doesn't require unloading after use you can get 2 of them, one of which is "clean", the other "dirty" or washing. When the "dirty" one is full you turn it on and let it wash while you take whatever you need from the "clean" one. Once the formerly-dirty one has finished it's cycle the roles are reversed and it becomes the "clean" one.
I've used these while working as a volunteer in a camp kitchen during work weekends, where we had maybe 20-40 guests eating a meal. You put dishes/silverware/pots/pans/whatever in a square tray, push it into one side of the Hobart, and pull down a lever to close the doors and start the cycle. They take a number of minutes that you can count on one hand... I seem to remember 90-120 seconds but I'm not sure. Stuff comes out clean and hot on the other side, and you want to pipeline this so it's one person with dirty hands feeding stuff in, and one person with clean hands (and thick gloves) pulling the square trays out, letting them cool, and putting the clean dishes/etc. away.
They release a huge amount of steam and they're wonderful for this kind of volume (20-40 people at a meal + all the cooking implements to support this). Larger than home use, though --- unless of course you had a mansion with servants. And I get the sense that maintenance and operating costs would be a lot higher than a regular plain dishwasher.
On one shift I was paired with a ex-convict. With the exception of the cooks themselves, most of the kitchen was staffed with high school students and ex-cons. The ex-con I was paired with was a dead ringer for Roger Daltry. I was on the "dirty" side and he was on the "hot" side (because there is a pecking order in even the worst jobs), and for some reason, he wanted _me_ to control the opening of the door. I think the reason is that this guy was high all the time and would space out unless something grabbed his attention. Anyway, I made the mistake of opening the door a bit too soon, when the machine was running, and it blasted this guy with steam. I remember him yelping in pain and then glaring at me angrily. One of the line cooks said something along the lines of "we try not to kill our dishwashers" which probably stopped the guy from punching me.
It's a beast of a machine. A little out of place in an ordinary household kitchen...
(They also have a fridge and then two pull out drawer units, one is for keeping extra snacks frozen things (like ice, ice cream, juice etc.) and the other is for veggie / meat.)
The downside of low tech solutions if many people touch it (i.e. not just the janitor or rostered staff) is that someone can still add their shared mug to the dishwasher just after a cycle's complete, causing the entire batch to be considered unclean. Or in your example, someone deciding to flip the sign but not emptying out the dishwasher.
Then again, these are little things that people have learnt to make do and just live with, and I'm not sure it's worth paying 2x or 3x, or even 20x the price just for fancy feet, like what the article thinks people might do with a fancy oven.
That doesn't help, however, if users are lazy and don't unload the dishwasher after opening it to grab a clean plate or whatever.
It's a nice feature that can be added with existing sensors and one line of logic in the uC. Another one I noticed recently is garage door openers with the photo transmitter/receiver ('beam') to stop the door if someone blocks it can use that same beam to turn on the light if broken when the door is up. Handy if entering a dark garage from outside.
The cycle-to-volume ratio is as bad as it could possibly be. Conventional dishwashers recirculate water as they wash and rinse. I imagine there's an mx + c formula to how much water is needed (c = enough water to prime the pump or whatever). So compared to a normal size load, you'd be wasting that constant amount of water.
The wash is also likely going to follow mx+c (c = time for grease to break down, time to rinse, time to dry etc). You can wait a few hours for a whole set of crockery. Can you wait a few hours for a single plate?
Commercial "passthrough" dishwashers work very differently. Manual mechanical action with a spray, plus a quick wash, sterilise and rinse. At that point why not wash your single plate by hand?
One pot, no dishes. Each roommate has to keep track of their private spoon. Greedy "clever" roommate who shows up with a liter ladle triggers a spoon fight in the kitchen. Eating from pot by hand is corrected by rapping their knuckles with your spoons. Eventually, all the glassware ends up broken, and some bozo threw out all the used red solo cups, but luckily, the kitchen faucet has a spray attachment.
“Perfection is achieved, not when there is nothing more to add, but when there is nothing left to take away.”
― Antoine de Saint-Exupéry, Airman's Odyssey