As I've said, the 3-6 months was based on my observation in this forum. If you go to each month's thread you will some cases of required officer review. Unfortunately, there is no dedicated thread this one, which I think would be a good idea if you can start it.
I got my MR on Nov. 6, 2014. Did the medicals on Nov. 10, 2014 and got my eCAS updated (Medical Received) on Nov. 14, 2014.
The updates on Feb, on the other hand, were my RPRF received and paid on Feb, 17 and eCAS changed to "In Process" on Feb 19, 2015 (with app processing started on Feb. 16)