They only list the resorts in active sales on the site but also sell points for sold out resorts. You just have to call them to find out what they have available or what the wait may be for what you want.
They re-sell them as "new."
While they only promote the newer resorts that still have lots of points to sell, you can call and buy into almost any resort as new. (The main exception being Grand California Villas which has a wait list to buy new).