The 48F/43R for oversized tires isn't too far off from what the rear tires "light load" button's reduced tire pressure TPMS threshold of 65F/45R used to be for the 2012 Dodge Cummins on the factory sized Load Range E tires vs their heavy load higher tire pressure TPMS threshold. FCA no longer offers this feature on the 2500 and so the factory tire TPMS PSI threshold is set for a heavy load. Alfa though allowed for the adjustment to that heavy load TPMS threshold.
Tire inflation/ light load button
https://www.cumminsforum.com/forum/showthread.php?t=1053562
Since our newer Power Wagon's have a lighter 6.4L engine than the 2012 Cummins, one would expect a lower front tire PSI setting than the 60F stated on the door decal when under light load. 50F isn't unreasonable which isn't far off from the 48F for the oversized tires. The 65R stated on our door decal for our Power Wagon factory Load Range D tires also appears to be for a constant heavy load application. Under light load it should be similar to 45R as it was the 2012 Ram 2500 Cummins. Not certain that the factory lower Load Range D tires would be stable at a lower PSI though. I am currently running Load Range E factory stock width tires which due handle fine at the lower PSI.
Sure the Power Wagon may get some better gas mileage running the factory sized tires at 60F and 65R per the door decal, but it's at the cost of wearing out the centers of the tires faster than a possible more even wear at say 50F and 45R when it isn't carrying a heavy load.