There actually are warnings concerning availability of rooms in the public offering documents that were provided by Disney at the time of sale. In the declarations, Disney explains how the point system means any member can reserve any room at any time of the year and then warns that all reservations are on a first come first served basis and there is no guarantee you will be able to get the reservation you want, and you are encouraged to reserve as far in advance as allowed to be able to get your choice of vacation homes and times. See, e.g., section 4.2.b in the declarations. The multistate POS, which deals mostly with reserving resorts other than your own, also mentions that Disney does not guarantee you can get a reservation and states that Disney may in the future add new resorts to the
DVC system without your consent, and that doing so could result in many new members competing with you for reservations at your own and other resorts. It also declares that reservations are on a first come first served basis, that there is no guarantee you can reserve what you want, and that the longer you wait to make a reservation the less likely you will be anle to get it. See, e.g., Multistate POS sections II and III.4.
DVC cannot legally sell memberships where the number of points sold would exceed the number it takes to reserve all the rooms for a year. I did a check of BWV's public filings on its units and total points for each and all of the units, which would include the share of points that would be kept by DVD (the 2% to 4% of all the units), which showed that the total total number of points created for BWV was a little less than it would take to fill all the rooms for a year if you assumed all 2BRs were reserved as 2BRs and not separately as studios and 1BRs. In other words, Disney actually "undersold" the resort in that it did not determine total salable points on the basis that those 2BR lock-offs could be reserved separately as studios and 1BRs for a higher total of points than reserving a 2BR.
What you are seeing now for Oct to Jan is a culmination of many factors that have developed over the years. Late Sep to marathon weekend in January has become the high demand season at WDW and demand during that time makes most of the rest of the year look like off-season. Most of the rooms at near park resorts are gone before 7 months out, and even SSR is disappearing some days during that high demand season before 7 months out, and only hope, prayer, and diligence in constantly searching availability, can possibly get you a studio anywhere during that high demand season at 4 months out or less.
Factors that have contributed to that high demand, including demand to the ultimate extreme for studios, include: (a) the ever growing popularity of Food & Wine, Halloween events, and Christmas decorations and related events; (b) the low, choice or adventure season points needed for most of the time during that high demand quarter; (c) ideal weather most of the time before you get to December and even then it is usually OK; (d) the ever growing, aging population of DVC members who are no longer tied to school schedules because kids are grown, no longer need rooms larger than studios, and now choose that period for reasons (a), (b) and (c) above; (e) the ever growing population of members who own 100 points or less, can get only studios, and highly prefer low point cost seasons because they have bought low point add-ons in the resale market, a market that has over the years become so much easier with the development of the internet, or have purchased from Disney since the Great Recession of 2008-09, when it lowered its point minimums to 100 and sometimes as low as 50; and (f) there are now a lot more members competing at 7 months out for the highly desired, "close to park" resorts. Moreover, in the last several years,members have become far more aware of the high demand season, including because websites discuss it and you can now see availability on the member site, with the result that more are reserving their home resorts at 11 months out while reserving the possibility of switching at 7, and most who attempt to reserve a non-home resort during that time are making the attempt at exactly 7 months out.
Disney obviously did contribute to the high demand during that quarter but not in an illegal manner as far as I am aware. It set the points at the choice and adventure season level for most of that quarter and has not done a reallocation to lower demand. It created the WDW events that have caused high demand for that time. It built many new DVC resorts increasing the total membership. It did contribute to the over demand and the legal "oversell" of studios by: (a) creating, beginning long ago, low point add-ons that could be resold to new members; (b) lowering the minimum point requirements for new purchasers from DVD to a level where the purchasers could get only studios, while coupling that with (c) a 50% increase in the price per point in the last six years during which inflation has been less than 2% a year, thus making it more difficult for purchasers to buy more points than those needed for a studio, and (d) creating resorts in VGF and Poly (and soon Copper Creek at WL), where the price per point and the points needed per night are so high that most can buy only enough points to get a studio, while DVD sells all those points for larger, but outragiously expensive, signature rooms, like GVs and bungalows, to members who can afford to buy only enough points for studios, thus creating a much larger pool of members who are seeking studios both at the 11 month window for their home resorts and the 7 month window for others.