Perhaps it is the angle, lighting etc., but the black portion of the paint scheme on the panel looks similar to the inverted trapezoid side/rear window on the Gremlin. The black outline seems to indicate they were trying to unify the actual side window on the Pinto wagon and a faux window that was painted (or decal?) on. I never noticed this before.
I did a Google search of cruise wagons and found a few that were solid color. The side windows does look rather abrupt, square and somewhat small (in comparison to the rear panel) with the port hole looking too far rearward.