My personal sense is that the OP's issue was likely more MS employee's not knowing what they can do rather than an attempt to withhold rooms. Disney, as noted, is subject to the same 11 month reservation window as the members when reserving rooms covered by the percentage of the resort Disney owns or gets via other means such as trade outs or foreclosures. It can set aside room space for maintrenance and refurbs even beyond the 11 month window, a factor BCV owners may have noticed for this year when rooms tended to fill somewhat quicker than prior years until in August when BCV suddenly became available during Sep to Dec because rooms were put back into service because this year's refurb was changed to next year. BCV owners are, of course, seeing the same somewhat limited availability issue now for 2016 reservations due to the scheduled refurb for 2016.
However, Disney's ability to reserve 11 months out does give it at least the opportunity to do some predatory reserving. Nothing appears to require it to actually have renters to put on a reservation at 11 months out and thus it can reserve something 11 months out and later add a renter. Moreover, the same-as-member rule means it can reserve any size rooms for any season and it is not required to spread its reservation time throughout the year or throughout the various size rooms. In other words, it could, for example, at exactly 11 months out, reserve all the AKV club level rooms for Christmas, and then later find renters for the rooms, because its ownership level in the resort obviously gives it enough points to be able do that. It is possible its fiducuary obligation to the members could be construed to prevent Disney from doing that but there is nothing specific in the official documents to prevent it.
There is one occurrence I found a few years back that indicated to me that Disney may have been trying to avoid the 11 month window rule and at the same time do some predatory reserving. At exactly 11 months out from the Sunday before Thanksgiving, I went online to see availability for AKV rooms for Thanksgiving week. Club level studios and 2BRs were already missing the Sun through Thurs, an understandable probability because there are so few rooms and you can reserve up to 7 nights from date of arrival. However, what I found strange was that the Jambo GV's were shown as full for the Wednesday and Thursday of Thanksgiving week but the Sun, Mon and Tues were open. Two thoughts occurred to me: (a) it is highly unlikely that any GV's would be designated, 11 months in advance, to be out service for Thanksgiving night and the night before; and (b) it is not possible for member reservations to fill that Wed and Thurs at 11 months out from the Sun unless the Sun, Mon and Tues were also shown as filled. In other words, my suspicion was that Disney was taking GV's for its own rental use for those two nights before the 11 month window even opened. I sent emails to MS and to
DVC Member Satisfaction asking for an explanation. I received back the typical we have received your email and response will be coming later. No response ever came. I have checked other holiday times for possible similar occurrences since I sent my emails but have not seen a similar occurrence at any other time.