Villas come from different inventory pools.
There are units (or sets of points) owned by DVD. Those are not available for member booking except through things like "developer points" offered sometimes with purchase. Also, with a new purchase, sometimes guides will be able to pull from this inventory to get you a room when nothing is available. Most of this inventory DVD turns over to CRO and rents out in return for profit. Disney will try to sell out a resort to 95-98% - keeping the remaining room inventory for maintenance. They don't intend to keep any rooms to use for CRO - although currently I'd be willing to bet they have ample inventory at all resorts due to foreclosure and default.
There are points owned by members, but which have been returned to
DVC in exchange for a trade. DVC then sells these points to CRO(or trades them out through RCI) to pay for our non-DVC options. If you've ever thought about cruising on points, this is what makes that possible. These points and their associated units are not available to members.
There are points owned and used by members.
There are points owned by members, but not used by members. At 60 (?) days out these are turned over to CRO and they try to rent them. This is "breakage" and the revenue gained here offsets member dues. These units can be reclaimed by member services for a short notice reservation - if they are available. However, most of the rooms you'll see as CRO inventory are DVD points or points from trades, so if you see rooms on CRO and there is "no room at the Inn" using points - it is not a given that the points can be reclaimed - more often, they can't.