RE: Passenger Van or Motor Home in Washington

You encountered what others have here in Washington have in the past couple
of years.  At one point in the past Washington refused to license a Westy
as a Motor Home.  BUT, the RCW (Revised Code of Washington) can be read to
make the Westy a Motor Home.  And recently people have encountered just
what you did, it depends on who is processing the title change.
I'd try another license station, you can find them at the Washington State
website.
For info, my '90 Westy is licensed as a passenger vehicle.  Came out that
way 13 years ago when I first bought it.  But the tag on the side says it
is a motor home in California where it was first sold.
There can be advantages to being a Motor Home when it comes to insurance.
You might check that out.  But the annual fee for a motor home IIRC is a
flat $110 plus any local vehicle taxes.

AQgain, welcome to Washinton.  And get used to the 'tax and spend'
mentality by our fearless leaders :)