Check out the discussion: https://www.youtube.com/watch?v=jHP942Livy0
That's just simply false. Read your dishwasher's manual. It'll tell you not to pre-rinse dishes.
Perhaps it's because there's a government program requiring it's disclosure and specific testing process?
If MPG labeling laws go away, what makes you think Ford will continue disclosing those values? And if they do, why wouldn't they start declaring MPG values driving downhill in a windtunnel giving the vehicle a tailwind?
You don't have to look too far to find those examples. Go to your local dealership that has some of the super duty trucks for sale. Notice how their spec sheet where the MPG is disclosed says "MPG testing not required" or something similar. Now how are you supposed to compare two trucks from the same brand, much less across two brands?
No third party certification is involved in those vehicles. Why do you think a third party would get involved in passenger vehicles if we relax the disclosure laws?
Information on performance is usually provided by third parties like Consumer Reports, Car and Driver, and other review services. Government provides and mandates quantitative statistics as a public service; private parties take care of the qualitative and subjective analyses (i.e., opinions).