I feel it is a mistake to try to compare RV dealerships/ maintenance/ service to the automobile industry.
One is a matter of scale. For every new RV shipped, over 15 new cars are shipped. There are more models and variations of RVs than automobiles.
RV manufacturers do not standardize their product line like automobile manufacturers do. You can find different components installed in two new same model/ mfr RVs sitting side by side at the dealership. Different components because supplier X had version one available for the build week for the first rig and another version for the week the second rig was built.
RV manufacturers seldom warranty the entire rig. You have to talk to the company which made the axles, the frame/engine in motorized rigs, the furnace, the ac units, the fridge, etc.
RV manufacturers don't create detailed service manuals, assembly manuals, etc. They don't stock millions of dollars worth of spare parts at regional warehouses or dealerships.
Buying an RV and comparing service is much more like buying a home from a tract builder and comparing their service.