I think that's the point. Relative mpg measurements are obviously too difficult for many to understand correctly. Changing it makes it so even that crowd can judge relative fuel consumption accurately.
So the question is which measure do you consider more relevant: Fuel consumption or fuel efficiency?
Fuel consumption asks "how much fuel do I have to consume to go a certain distance?" Fuel efficiency asks "how much distance can I get out of a given amount of fuel"? If I have a fixed size gas tank (as all cars do), and I want to know how far I can go on that tank of gas, then fuel efficiency -- rather than fuel consumption -- is more important to me.