What I know is: The fact that they have sent FP to a huge number of applicants means they have done a lookup/Query on cases within a specific date mostly driven by the Processing date. Having done that, They went and started sending an RFE on a set of cases which I believe is random but I believe before the Dec time frame and add to that some unique criteria on the cases (which we don't know).
Where this theory fails to apply, is that some people with a processing date around or before DEC haven't received anything yet and that is what I call exception cases thats all.
Bottom line, This is really frustrating however we look at it and try to understand it... and the conspiracy continues....