I would be willing to bet that they have sales projection models they are looking at and they need to sell x amount of units before enough inventory is moved into the
DVC from the developer. We all have to remember that the developer owns the inventory until it is sold, then it is moved into DVC. While there may be a whole bunch of rooms sitting there unused, if it is not in DVC inventory, they can't use it for reservations. The developer can rent it for cash though if my understanding is correct. I don't think that the advantage is such a big deal and they probably have so few SSR owners that it doesn't impact the DVC inventory available to the rest of us. It is not like they are getting this huge head start, and if there is not enough inventory available for the SSR owners to book at their home resort they would be upset. If I spent 15K and couldn't book my own resort because it was opened up to the general membership and they jumped on it because it was new (and you know lots of people will want to try it out before they bought more points) I would be pretty upset.
If the inventory is not there to let people book it you can't really blame them for not letting you book. Since there is plenty of inventory for DVC the few SSR people won't have any impact on reservations (probably until Feb., when they opened SSR for everyone else to book)
It is probably just a case of the numbers can work so why not let them do it rather than lets stick it to the existing owners.
I have found DVC to be pretty reasonable and fair and this is probably just a case of trying to let some people enjoy something they bought a little early, without impact to others. A little magic if you think about it.
The impact is nominal to the rest of us so we should be happy for them that they get to enjoy what we have had, and not be upset about something someone else has that we can't have.
Oh, and BTW, I don't own SSR.