If a datum element (such as a reference plane) is not perpendicular to a view, then the datum element does not display in the view.
For example, the following floor plan shows 2 reference planes, indicated with dashed green lines. The reference plane on the left intersects the section line at an angle. The reference plane on the right is perpendicular to the section line. Because the angled reference plane is not perpendicular to the section line, the plane does not appear in the resulting section view. However, the perpendicular reference plane does display in the section view.
