I'm not sure how they organized it...I really wish they would tell us our ranks, but I guess with all of the changes in acceptances/denials, they would literally send out an email every single day. From what I've gathered, most schools already know who they're going to pick before they even hold interviews; they just use them to see who is willing to travel/find out info about the school/etc., so you might be right about the earlier you got moved off of the interview wait list-earlier acceptance wait list movement correlation, but who knows. I'm just hoping enough people decline the school, and that I'm high enough on the wait list to gain acceptance sometime in the next month or two!
The good thing about them only giving a week to decide is that, if there is movement, we'll probably know sooner rather than later!