A non-ranked waitlist is NOT a non-ranked waitlist. A non-ranked waitlist is simply a ranked waitlist where people can be skipped over. When you have hundreds of applicants, they aren't going to honestly review every single file.
You see, the important thing to realize that who will be picked may not be ranked, but the order in which people who eventually do get picked is. For example, let's use letters of the alphabet where earlier letters are "better" than later ones.
In a ranked waitlist, the order of who gets picked is A, B, C, D, E and so forth.
In a non-ranked waitlist, if C is picked, you can't assume A and B were, however if you know that F and S where BOTH picked, they decided on F being accepted first. In this case, it appears to be "non-ranked" because people automatically assumed that every letter before F will be picked before F is, but that isn't true.
Non-ranked waitlists are NOT about who gets into a school, but when!
See what I'm getting at?