To your first question, no, you'd have to contact Toyo and see what they think. I got those particular numbers out of an old study report. But I wouldn't expect dramatic differences between tires designed for the same goals. I'd expect just small differences between ATs.
But also, notice that those are all different tire types I listed from that report. The Goodyear Integrity is a basic all-season designed for mileage, the Uniroyal is tour-rated kind of middle-of the road tire, the Bridgestone is designed for extremely smooth ride and low noise, and the Pirelli was a "comfort" tire.
So those four tires progress from stiffer to softer rides, which probably explains the increase in coefficients.
To the second question -
The Toya AT is a pretty stiff tire, but the tread is more aggressive than any touring tire made, which increases the rolling resistance. You'd certainly get better mileage from highway tires. LT highway tires have smoother tread, and smaller gaps, if any, between successive tread blocks. Here's a pic of Nitto Dura Grappler tread, for example. Of course, they don't look as cool as something like the ATs. The Dura Grappler is designed for high mileage.
One thing I do believe is that Ram had to run their mileage tests on stock trucks in the trim model, and all the Rebels are sold with the Toyos. So I don't think that the tire explains any real difference between the tested mileage showing on your sticker and what you actually get. (I might be wrong about the tests, it's just what I think is supposed to be done.)
But, what I do know for certain will effect mileage:
Low tire pressure (1 psi on a car tire = .7 to 1.2 mpg loss in past testing) With our higher pressure, the effect is lessened a bit, but still around half that.
Driving steadiness (steady foot = less changes in speed = better mileage)
Speed over 50 (+5mph = -3% to -10% mpg)
Speed over 65 (air resistance is high enough at that range that MDS starts to kick off over 65, as much as 8% mpg loss)
Speed over 75 (air resistance starts forcing mileage down even faster)
This chart is of the mileage I got when I ran a long series of tests. The blue line with the marked dots are from monitoring the truck computer over a number of miles on relatively flat highway, to see the highway mileage. You can clearly see the large drop in mileage between 65 and 70, about 7.5 or 8% difference? That's where the MDS was tending to shift off, depending on minor grade changes and wind direction, and of course how steady I was. The thin green line is just a projection of what the mileage might have been
if MDS had stayed on. And the purple line is where the mileage might be
with MDS disabled. I never bothered to actually test that.