Since Superchief noted in post #5 that about half of the old building is weeks owners, that means that Crystal Shores opened prior to the DC Points Program inception. They had already sold about half of that building as weeks when the Points program started. Therefore, the only inventory that a weeks owner is entitled to occupy/use - at any resort - is that which was sold as weeks. After the Trust was created, no new weeks were sold and any unsold and/or new-build/acquired weeks deeded over to the Trust. Now Trust owners have rights to use those weeks, not weeks owners. So it is, in fact, very fair. Weeks owners have full legal access to weeks inventory and Trust owners have full legal access to Trust inventory. The only way for a weeks-only owner to get access to Trust inventory is if Marriott Vacations opts to deposit some portion of their Trust inventory into Interval International.
Think of it as basically two separate resorts under one roof - one, a resort made up of weeks owners; and two, a resort owned 100% by the MVC Trust. At Crystal Shores, the new buildings are adding inventory to the Trust resort. The old weeks resort quit growing in June 2010, and has almost certainly been shrinking since, due to foreclosures, ROFR, and repurchases that MVC exercises to transfer into the Trust.
It's also similar to the old legacy timeshares in some other non-Marriott systems where two developers operate units within the same complex. Maybe Developer A started development of the resort, but then sold undeveloped property and/or unsold units to Developer B. People who purchased from Developer B do not have rights to occupy/use/trade units that were part of Developer A's units that share the same property.