I think I see your point; clever. The site could show the message and only then send the mail asynchronously. I guess that's why you said most implementations.
Queuing up an async message still takes time. As does reading a row from a database and materializing an object. So "most" is really probably nearly all unless they take explicit steps to make sure the same amount of work is performed in either case.
Yes, or sleep to elapse a time that's longer than needed to queue up the async message, say half a second, before returning the message to the browser.
