It seems that we can take this as internal evidence that more people are just 'walking away'. Now we have a procedure to handle the cards in this event -- assuming the body knows where the individual moved.
What I really love about this letter is how the Society puts all the liability for what is written in the introductory letter on the local body. Sure, they tell them to include basic biographical information, no surprise there. But then they answer a question with a question: "What informati o n s hould be conveyed in the lett er of introduction ? A s k yourse lf : What information would we want to receive if this person were moving into ou r congregation?"
A typical (Reasoning-book style) non-answer that places all the risk on the local elders!