Right you are. This does work... sometimes. Today our group waited for nearly an hour. Friends were called upon to join the queue and waited in the queue while our group waited for replacements. This is why I am posting.
I can assure you that I am not the only person to experience this issue.
I have encountered this many times and every time the person joining the queue failed to tick the ' join in-progress' checkbox. This checkbox is not the same as the one from flashpoints, it is in the operations window of the groupfinder (where you can select which ops to look for). After they checked it they could join our group.