I researched this when we moved back to OR from CA a few years ago. I came across a section of the law under large motor coaches that dimensions are measured when extensions ("tip outds") are closed. This makes sense - a large motor coach with a side extension open is too wide to be on the highway without a special wide-vehicle permit and all that goes with it.
See
http://www.odot.state.or.us/forms/dmv/464.pdf
"The width of 8.5 feet is measured when any expansion sides or “tipouts” are in the usual travel position. The length is measured from the foremost point of the trailer hitch to the rear extremity of the trailer body, not including the spare tire. Tent trailers are measured by overall length when folded for travel."
While height is not covered, it would be hard for OR DMV to legally require height to measured with the "tip out" roof open.
The problem is that when an OR DMV agent is asked, they will cover their butt by saying it's a motor home. This makes sense - suppose a cop cites you for not having a motor home license and you argue in court that some OR DMV a certain OR DMV agent said it wasn't a motor home.
I'm pretty sure Jeff goes the license route because it would be expensive to challenge OR DMV should they come after him - I can't blame him. OR DMV would probably try to charge him the license fee plus penalties for every FWC sold.