Spatial join is outputting seemingly incorrect result in ArcMap

Question

I am attempting what I thought was a straightforward operation in ArcMap. I have a polygon layer where some polygons overlap. I also have a polyline layer. I would like to spatially join the polygon layer with the polyline layer using a "WITHIN" relationship.

The objective is to make sure every polyline which is either fully or partially within a polygon layer takes on the attribute from the (partially containing polygon). This is what the spatial join dialog looks like:

What I do see, however, is that many polylines do not obtain a containing polygon attribute and get a 0 instead. This occurs mostly in polygon border crossings and when a significant portion of the segment lies outside the polygon.

Which is very confusing because it implies that "WITHIN" and "COMPLETELY WITHIN" have the same behavior? I thought that "WITHIN" implied that even target features partially within the join features get matched...

What am I doing wrong here? Is there another way?

Answer 1

A line crossing a polygon border is not within. Use intersect instead:

The features in the join features will be matched if they intersect a target feature

Look at a description of the spatial queries here