When the WhatsApp 24-hour window is closed, agents must send a template first, wait for the customer to reply, and then send the actual message. The customer wants to attach the real follow-up message to the template send, so it goes out automatically the moment the customer replies and reopens the window. It would work like a scheduled/delayed message, but the trigger is the customer's reply instead of a time. This saves time for agents and customers, who get the answer immediately without waiting for an agent to see the reply.