Please help bring me up to speed: By "lists," do you mean some kind of list of schools which costs Ashworth nothing to be listed there; or are you talking about a listing that is actually advertising for which Ashworth must pay? If it's the former, then maybe there is a reason to wonder and to follow-up; but if it's the latter, then it could be as simple as that Ashworth figured out that being listed there got them so few students that it wasn't worth the money it was paying for the listing... in which case it's no big deal.
I believe both used to be listed. However, Gregg may be onto something. This may be entirely proprietary (some have obviously garnered more of a listing than others). I figured there would be more response since this guide has been lauded by many on this board.