Imagine a plane that has been split and then rejoined. If IncludeUnweldedEdgesInNgons is set to true then you would get an ngon with 6 vertexes, the corners and one on each edge that was split. Setting this to true would remove those 2 vertexes from the interior of the edge. TODO This is not hooked up yet, Dale hasn’t made this available yet. See RH-30673.