As you hit the 'post this message' from Google you get the 'good' reason. They explain to you that the message will appear in Google with a delay because the need to archive it and to be able to show it (from search - that's how Google is 'built'

. On the other hand, the message posted on Google can be immediately be retrieved by other servers and, depending on their refresh rate, it can appear in a few moments. So those who use other servers see you message and can reply. You will see the message and the replies after many hours.
Michel de NostreDame