Not speaking for them, just generalizing.
'Less fuel' can be somewhat of an ambiguous term. The general public doesn't understand the difference between better fuel economy and better MPG's. Fuel economy is the mass amount of fuel required to produce X hp. MPG's are how far you go on a gallon of fuel. The two aren't necessarily related.
*pulling #'s out of my ass
Take a Geo Metro and a Chevy P/U. The Metro got around 45 MPG and made 50hp. The Chevy truck gets about 17 MPG and makes 300hp. 50 divided by 45 = 1.1. 300 divided by 17 = 17.6. Meaning that per gallon used the Chevy is more fuel efficient than a Metro. Even though the Metro gets better MPG's, most all of which has to do with weight of the vehicles. The best example of a good balance I can think of is a newer Corvette. 400 some odd hp and you can get 30+ MPG highway with them pretty easily. Very efficient car in all regards.
Long winded but what all that means is the SCT may be thinking efficiency vs MPG. Though it is possible to improve both if you find the right tuner to help you.
For example if you wanted better highway MPG's you could tune leaner closed loop or back off the timing a bit. I can't recall the numbers off hand but there is a formula to find how many hp it takes to sustain a certain speed. IIRC 60mph is something like 30hp for the average newer car. So it doesn't take a ton of power but you need enough or the engine luggs and you end up using more fuel.