I believe the thinking behind these numbers is they want people to have enough points to actually be able to book a room. If you only have enough points to book a studio in low season you will come away disappointed. Which is why they will let resale owners add 25-50 points.
I think the 150 reflects that new DVC resorts are going to require more points to book. (In addition to Disney straight up trying to capitalize on the demand for DVC). Copper Creek may be the last steal on point value!