You are right. It is coming to the point of weirdness. Note that some of our friends before August change also got the E-mail "AOR" as back as June/July and they have also not got any response.
Clearly, there is something which is associated with the applicants, some factor, of the application based upon which an E-mail AOR is given than the paper AOR. Haven't found anything yet specific.
It could be my wild guess that those who have done any Education in Canada are getting Email AOR or their education level assures the CIC that he/she can handle instructions through Email. My hypothesis is that the CIC would make it sure before that the person is computer friendly so as to read the Discover Book online. That doesn't mean all those mail AOR are not computer friendly but there has to be some factor which differentiates one from another.
Keep your thoughts flowing friends