I think the inventory was pretty thin when BCV was close to sellout and before SSR started pre-sales. That is why they scrapped Eagle Pines for SSR because SSR could be ready much faster.
Yeah, SSR started selling around August or September '03 and buyers there weren't able to use their points until May '04 when the resort opened. DVC did have a few BWV (from refurb of old model rooms) and Vero points they were selling in the fall of '03 but after those were gone the only real option was to buy SSR and wait as many as 8 months before the first stay could occur.
Later throughout SSR's phased opening there were other periods where DVC was in a "pre-sales" mode...selling buildings that were not yet open. But, IIRC, they compensated for that by giving out the infamous Developer's Points which could be used immediately.
Similarly early buyers at AKV couldn't use their points until the unit were available, and I suspect the same was true of most prior resorts--DVC doesn't wait until the doors open to start selling.