Cash reservations and Point Reservations are different pools of room availability. The largest portion of cash rooms become available after a
DVC owner trades out of the DVC system for Adventures by Disney, a cruise, the Disney Collection, or other "cash equivalent" trade. Basically anything other than RCI or an actual DVC Resort.
A room representing the points used for the trade is turned over to cash reservations, the cash received by renting out the reservation is used to offset the cost of the trade destination.
Also, any unsold points and points that Disney reacquires though default are not owned by DVC Members, and the rooms those points represent can be used by Disney for cash reservations, promotions (like when the family from Home makeover goes to Disney), or basically any way they wish.
Disney also retains about a 4% to 5% ownership in the DVC resorts to use for maintenance, if necessary. If those maintenance rooms are not down for repair, they can be rented for cash.
Any DVC rooms not reserved on points at 60 days are also turned over to cash. The cash received helps offset our dues in the "breakage" income column. These breakage rooms can be reclaimed by DVC if needed for point reservations, if they are not already reserved for cash. However, breakage is the smallest pool of cash rooms, so very few are available to be reclaimed.