Hi Mel,
due that I wrote it long time ago I'm really not sure if I remember well what I found during my testings
Anyway, what I mean here is to pay attention that Joomla changed the workflow (messages has been deprecated), read carefully the GitHub ticket and it's related tickets.
The same should happen during Login/Logout through SCLogin and JFBConnect Social Login (maybe they are calling Login/Logout SC language strings)