[whpalmer4]

Well, again, you are asking it to group by Due date, and that is what it is doing. As it happens in this particular case, the items in the no due date group all share the characteristic that they have been flagged, but if you had set the action selector to something else, that wouldn't necessarily be true. I would argue that to only mention the flag status for those without a due date is a bit misleading, because it suggests that the items in the other groups aren't flagged.