I'll take an educated guess: self leveling rear air suspension (this is an option on the euro Ducato).
Does that option get labeled for motor homes in Europe? Air suspension would have broad appeal, so why would they limit its market by labeling for "motor homes" other than to be consistent?
It's interesting they see a difference between a motorhome and other vans. From my perspective the biggest difference is that an RV, once built, doesn't run empty at all like a regular van. Because of this it would allow engineers to better tune the suspension for a vehicle that weighs around 8000 to 9000 pounds all the time without worrying about it riding too harsh when empty; which is typically around 5000 pounds for an empty ProMaster. A RV suspension may include stiffer springs and or shocks, and maybe slightly different ride height. On Winnebago Travato the Onan generator is only 6 inches from pavement. If van were loaded down or towing I'd be concern with it being even less.
Or it could be slightly higher Gross Vehicle Weight Rating to compete with Ford Transit with single rear wheels.
I obviously don't know either but I'm glad to see RAM is taking the RV business seriously enough to offer specific packages.