I can't say for sure, as I'm not the one sending the letters. Mine mentions a "select group" of some kind, but I can't speak for anyone else.
Right, I think everyone's mentions that they were in a very select pool of applicants the committee wants to admit, but doesn't know if they will have the space for. I don't have my letter in front of me, but I know it said something to that effect.
We are probably reading way more into this than we should. They said the list isn't ranked. It isn't, but if they see their seat deposits are on the low side, lacking a certain URM group, LSAT score, gender, or geographic representation, they will go to those people who can fill the voids on the PWL first.