I don't think the sale of Aulani is mentioned enough in regards to its impact on DVC at WDW. They market the heck out of it at WDW and discounted prices to entice buyers to invest there, even when they had properties at WDW to sell. Many owners of Aulani will never or rarely go there, especially if they are East Coast US residents. They were sold on the idea of going to Hawaii at some point over the life of the contract, but "that doesn't really matter because with DVC 'flexibility' is the name of the game." "Stay where you want, when you want, in the type of accommodations you want."
That is a lot of points hanging out with people looking to book WDW DVC resorts at 7 months. Many of those individuals bought when "low point contracts" were available too. So that is a huge crunch on studios and 7 month window.
Lastly, remember that the idea of of DVC being sold as "Stay where you want, when you want, in the type of accommodations you want" really goes out the window when lots of owners are all clamoring for the same periods of time. Points are sold based upon the whole year, but the vast majority of owners want to use them at specific times of the year. This too creates a crunch.
All this adds up to the 7 month window, especially for those looking for studios, a massive crunch. This is why you buy where you want to stay.