In a Walkie Talkie conversation, when a message arrives while you are looking at the newest one, the messages above move up and the new one slides in at the foot. This happens for your own messages and for other people's. Nothing moves while you have scrolled up to read earlier messages, and on a device set to reduce motion, new messages appear at once.
The line "1 recording is waiting to send from this device." now appears only for a recording that could not be sent and is waiting for the connection, not while a recording is being sent.