I really have no idea...
I think it may have something to do with the VO and the organization of your application?
Mine was super, uber easy to navigate because I used tons of paper clips and manila folders for each section (sub-divided in to OWP, Sponsor, Principal Applicant, Travel Proof when I was living in the US, photographic evidence attached chronologically and labeled with post its, letters from friends+family, and what not
)
The agent started by telling me that "I'm not sure if I will be able to see your medicals because you submitted it only a month ago... oh, but wait... we received it on the 3rd"
I said, "Oh, that's great! Thanks for your help! Is there anything else I need to do at this point?" because when I called, I said I just wanted to verify that my medicals were received.
She replied and said, "They are currently doing your background check so no, there is nothing more you need to do and you just need to wait for CIC to contact you."
I know that background checks are part of the 2nd stage so even though I don't have an official letter confirming my AIP, I know that my initial assessment has been completed. Just gonna wait and see what happens!
If CIC has not already contacted me by March, that's when I'll make my next call, I guess.
Good luck to you and everyone else! I have a feeling that October is going to bring some good news for most of us!