Don't know if I'd call it "very inefficient"...probably "less efficient."
Yes you get the greatest value by using points for DVC resort stays but there is still some value in other uses. Cruises tend to yield $7.50 - 8.00 worth of value for every point. If your dues are around $4.50, you're still paying less for the cruise.
And the DVC initial purchase + dues are a sunk cost--you're committed to paying that amount regardless of when/where/how the points are used. If you want to cruise in a given year but don't really want to do a DVC resort stay, the reservation can be completed in a single phone call with OOP expenses of just $95.
Renting points are an obvious alternative for people aware of the process and willing to undertake...but many just don't want the hassle.
Overall I think we would be very surprised at the volume of points used for Disney Cruises and other non-DVC options.
As to the original topic, I received my Condo Meeting announcement / resort budgets for the 3 properties we own. If memory serves, amendments to the POS are typically listed under the bylaws amendments on page 2 of the notice. And there is nothing in here related to booking window / resale provision changes.
DVC can change administrative rules without actual amendments as long as they do not go counter to the POS. Some of the posts here suggested that DVC/DVD would use its absolute authority to amend the POS and impose even more radical restrictions. That does not appear to be on the horizon.
