That is a bit odd. But at least in my experience with my F150 and the Ecoboost motor, big tires dont really bother it. I went to 315/70R17 KO2's on my truck and it was a pretty minimal drama, unlike going to 285/70's on my GX460.I was surprised that a bone stock Colorado with smaller tires has the same diff ratio as a loaded Colorado with 33s
I think 3.42 gears?
285/70R17 is roughly 32.7 x 11.20
315/70R17 is roughly 34.4 x 12.40
Also, I was kind of surprised at how many RPM's it turned on the freeway. I figured with the 8 speed and the 3.42's it would have been lugging along in 8th, but at 70 mph it was spinning 2000 rpm or maybe slightly above. My old 6 speed F150 with 3.73's turns lower RPM's.