Section 5.2 on selection, page 237, in the 2.1 specification.
[…], but selection is based on the polygon itself, regardless of the setting of PolygonMode.
Section 3.5.4 on polygon mode, page 111, consistently speak about rasterizing the polygon’s edges/vertices as lines/points in the non-default polygon mode. Since selection is purely a geometrical selection, rasterization does not affect selection.