Still looking to buy my first RV but here's my take (I was going to start a new thread): I think they have potential for moisture damage.
Have only seen a handful of Class As and only two with driver-side doors. The first, an '03 Forest River Windsong, had rotten OSB floorboard at the rear of the door (and just aft of the pillar), as did the bottom of the pillar itself (vinyl had delaminated/bubbled).
Next was a '00 Winnebago (not sure of the model but a gasser). Pillar under where the shoulder belt attached was torn and felt lumpy. Fiberglass outside seem to have bulged out but uniformly).
Granted, these RVs are in a fairly wet & humid environment but it would appear that the door frame cutout is another way for moisture to get into the wall.