Nothing wrong with no security.
Suppose it's not connected to the internet and air-gapped. What's wrong with a "D" label?
As for home appliances, physics don't work that way.
Dishwasher tablets are standardized to work in a certain volume of water. I think it's something like 5 liters. Heating up 5 liters of water from 20 °C to 70 °C will always require 0.3 kWh. Pumping water with a 500 W pump for 2 hours will always require 1 kWh.
An AAAA model will require exactly the same energy in that intensive wash cycle as an A model. And that A model might actually have more usable low energy programs which might end up saving power in the long run.
I have an AA-qualified dishwasher. The newer model with AAA qualification was an extra ~50 euro. The testing method requires that the very first program after turning on is the one used for testing.
I used it once for only slightly dirty dishes. I didn't even bother removing them from the dishwasher since they were stained, and still dirty and wet (despite 1.5 hours of washing and 2 hours of "drying"). Using the same detergent, I set it for one hour quick program (same temperature of 50 °C), and the dishes were completely clean.
As for fridges, same physics apply. Assuming the same insulation, it requires the same amount of energy to remove 1 kJ of heat regardless of the energy saving features. I do have a nice AA model that works pretty well, but I bought it for the warranty (10 years for the pump which is the digital direct drive version). It's nice and quiet as long as it's running on gear 1-2 out of five. At 3 it's already as loud as my older fridge and at 4-5, it's loud enough to be heard, although fortunately it's just a humming noise.
I realize people buy into the hype, but standardized labels are for standardized conditions for standardized people in a standardized world.
Sadly, in the real world, there are no standardized conditions or standardized people. But standardized labels exist.