Fastpaddler,
You are overthinking it. Your Plateau is a Class B RV. It was "built as one unit in a factory." Just keep it simple. Class B started as a van, period, no matter how it was subsequently built.
For those with Class Cs (or B+ if you must) thinking they have a lot in common with Bs, just remember they have larger tanks, dry baths, lots of outside storage, different non-steel bodies, mirrors that overhang a standard 9 ft. wide parking stall and can't go where Bs can go no matter their length. As I said before, it is B-ness envy without the commitment and a lot of rationalization. Or put it another way, a B+ could try and follow me across the Going to the Sun Road in Glacier National Park from Browning, MT to Whitefish, MT a distance of 93 miles or save themselves the grief of shearing off their roof by going around 315 miles. To explain there is a 10 foot height limit which is critical going west with the rock overhang. Length is arbitrary there as they use 24 ft. Sprinter passenger vans for shuttles in the park. It is actually not that difficult of a road to drive.