Wow, that was good for a pretty hearty laugh. Their calculations are done in a manner that may seem scientific to some, but anyone that understands CFD, aerodynamics, ICE efficiencies, etc. will see right through it.
I like how they almost instantly equate the reduction in drag [at some fixed speed even though they test at 2 speeds] at 5% (is what they keep using across everything) into 5% fuel savings. Sorry, the game doesn't work like that.
Also, the results are difficult to quantify in the real world with so few miles and no real controlled, repeatable testing conditions to compare. The main problem is if someone puts a device that is supposed to increase fuel economy on your vehicle, you are aware of that, and you also want to make sure you increase fuel economy, you're going to end up driving in a manner that will increase fuel economy. It's that simple.
The main problem is the aero properties of our trucks. Wide tires, high ground clearance, house-size frontal areas, squared shape, big mirrors, upright windshield, large gaps and holes for cooling and fit and finish... all these contribute to our trucks getting terrible MPG.
Interestingly though, this isn't new tech and it's not unfounded. This was last used (that I know of) on a production car, the Mitsubishi Evo MR to redirect [turbulent] air from the roof to the rear wing.