Some of the owners who have owned for a long time might know the answer, but I do know that it's the only DVC resort at WDW that doesn't have dedicated 2BR villas.
I'm sure that the lock-off configuration provides the highest degree of flexibility for DVC to book rooms (and therefore get as close to 100% occupancy as often as possible).
Perhaps after building OKW they encountered some problems with matching the right number of dedicated villas to member demand? In other words, they might have had dedicated 2 BR villas that they couldn't reserve at certain times of the year since members wanted more 1BR & studios?
Just guesswork on my part. More interesting is that when they built VWL, BCV and SSR they added the dedicated 2BR back to the mix.