The room availability for cash has nothing to do with availability for
DVC points.
DVC rooms become available to general Cash reservations if
1) A DVC members uses their points for a cruise, Buena Vista, Adventures by Disney, or regular Disney resort stay. In theory, the member is booking a DVC room, then trading to Disney and Disney rents the room for cash to pay for the trade.
2) Developers and Disney inventory. Any "unsold" points inventory is developers points, thus can be used for sales promotions or can be turned over to Disney at the discretion of the developer. Also, Disney retains a small ownership in the resorts, even if the resort is fully sold...any rooms not needed for maintenance can be rented by Disney for cash.
3) Any DVC room not rented on points is turned over to Disney for rental at 60 days out. This class of rooms
can be reclaimed by DVC is they are not already rented by Disney. This is the ONLY class of rooms that can be reclaimed by DVC, and the percentage of the total Cash inventory for these 60 day turnover rooms is very small. Chances are the cash rooms are coming from one of the other sources, and can not be used by DVC.