That may have been exactly what the group owner thought they were doing. I'm not sure when Facebook switched over to "Add People to Group" instead of "Invite P

That may have been exactly what the group owner thought they were doing. I'm not sure when Facebook switched over to "Add People to Group" instead of "Invite People to Group," but I vaguely recall that Facebook groups used to do the latter, which is a behavior that, at least to me, makes a lot more sense.