I found the following video in another forum post where the video shows how enlightened (newer) SQL clients that support the redirect feature are redirected to the SQL instance where the AG listener is running because that is the primary replica in the AG at that time:
http://www.youtube.com/watch?v=A8lSl8nO1r4
That makes total sense.
What I can't find confirmation is if in the case of a legacy SQL client if the SQL client keeps talking to the AG Listener the whole time (unlike the redirected clients), or if something else happens. I suspect it keeps talking to the AG Listener name and IP address which "proxies" the requests to the back end SQL instance.
I apologize if I am not using the correct terminology, I am new to SQL 2012 AG and am trying to wrap my brain around a lot of concepts all at once. :)