IME, "queued" is a bit of a misnomer. When you submit a message, yes, it is technically queued for the OR servers to call the messaging API, but in practice, even though it's not exactly sent in real-time, the queue is processed nearly immediately.
So, yes, from a software developer's perspective, it's "queued" for sending, but from a normal person's perspective, it's effectively "sent" as soon as you click the button.
What you might be asking for is really an "Undo" option, like many email clients offer these days. However, this comes at the cost of introducing an artificial delay before the message is actually sent, which may or may not be desirable--to be honest, I think I would prefer there to be no artificial delay, because I've found that even taking 30 seconds too long to respond to an Airbnb message often results in my phone ringing from a phone call from an impatient guest who really wants the answer to a question right then. :)
