What is a Crosswalk?

On the steep hillsides of Seattle, many streets are built out as stairways, not as roadways.  One example is East Thomas Street, seen here in Google Maps:

East Thomas Street is a stairway both east and west of East Madison (the stairway in this view is hidden in the trees).

As you know, every intersection in Seattle has crosswalks, whether marked with paint or not.  People are allowed to walk across the street at intersections, and people driving cars are required to stop for people walking.  I've often wondered whether this intersection of a busy arterial and a walking path also creates a crosswalk.

As you can see in this shot looking east across Madison, this intersection is marked with a street sign.  The sign for East Thomas Street includes a walking icon to indicate this is not a street for cars.

Is this a real intersection with an unmarked crosswalk?  The sign attached to the bottom of the pole suggests that some people might think so.  But it directs people NOT to cross here:  "Use Crosswalk."  The arrow points up Madison to this intersection:

As we know, there are crosswalks here.  They are all unmarked, and people who drive cars on Madison ignore them, but there are crosswalks here.