To wade in here a bit, I don't think the North American usage of the "highway=motorway" tag has ever required that a road have freeway characteristics from end to end, merely that the segments tagged as motorway have those characteristics for a reasonable length. I really don't think an appeal to "common usage" flies here.

In WA 500's case, it appears the freeway is interrupted by a segment with two at-grades for maybe 15% of its length from I-5 to Fourth Plain Blvd. This seems somewhat analogous to the case of US 71 in Kansas City, where NIMBY opposition has left a section of the route without full access control. How is it tagged? See osm.org/#map=14/39.0107/-94.5474

Fixed.