I am just back from a 4000 plus miles trip through the Pacific Northwest. I use CoPilot Premium with the RV option switched on (and I use a Samsung Galaxy Tab 10.1" to run it on).
With it's 31' length (plus the carrier for the motor scooter would make it about 34 - 35' long), my motorhome had no problems at all to get through any roads CoPilot did send me to. I always have my TomTom running also, and if I would have some of the routing of the TomTom, I would have got stuck.
I also wonder why the RV product, because the premium product with the Rv feature turned on, seemed to be just fine for shorter Rv's.
Looking at their table, I have the feeling that the Rv product is mostly geared towards Europe and has not many benefits for the US user.