OK, first, anyone who wants to jump in and correct any inaccuracies is welcome to do so. I'm about 95% sure this is correct, but may misstate some of the details.
As I understand it, if you want to book a room at the Grand Floridian, the process works something like this:
1.
DVC accepts your points to trade into the Disney Collection.
2. DVC makes a cash transfer (on paper) to the Grand Floridian to compensate for the room. The GF has no use for DVC points--they simply want to get paid for the room.
3. DVC can then take your points and use them to rent out a room at your Home resort at the published cash rates. There is some element of risk involved in this process, which is one of the reasons that we don't get very good value for our points in trades. If DVC is unable to use your specific points to sell a room to a cash customer, the room is empty and the points have returned no value.
Remember, DVC sells enough points that each room at each resort could be booked 365 days / year (barring scheduled maintenance.) So, whenever a room sits empty for a night, someone is losing points--either a DVC member who didn't use their points, or DVC who is unable to rent the room for cash using points acquired in trade. Member actions like Banking / Borrowing or Magical Beginnings do dilute the true picture to some degree.
The above would be the reason for the weekday / weekend differential at the Disney Collection. In order for DVC to hold a cash room for a weekend with your points, they are using the same premium number of points.