Disney owns a certain percentage of DVC points themselves. I believe it is in the 2-4% range. These points are used to pull rooms out of service for maintaince, other allowed reasons, and also for Disney to sell the rooms for "cash" to the general public in the same way people reserve their hotel rooms.
For the initial chunk they are going to make available for the public to reserve, they become available no further out than 11 months from your stay.
IME, they do not suddenly load them all at exactly 11 months. Instead, they get gradually loaded within what is usually the 10-11 month window, but can be the 9-11 month window. It seems to depend on the resort, and even within a resort not all room types will load at once. So for example, at a particular resort the 2 bedrooms may become available one day and then a week or two later the one bedrooms and studios will become available. Doesn't make sense to me, but it seems to be how they load them into their online system. We've booked DVC rooms a few times directly with Disney and spent a few years stalking their website to get an idea of how and when the rooms load in preparation for our trips and while I figured out a few seeming patterns for the resorts we were interested in, there didn't seem to be much of a global pattern for specific "loading" beyond the less than 11 months.... I recommend you start checking each day when 11 months hits.
Over the ensuing months Disney will then have additional rooms that will become available to them to be able to sell to the general public. As DVC members trade in their points to do things like go on a
DCL cruise, those points then become available for Disney to sell to the public. So periodically new availability will pop up. Also, of course, people change their plans, so that can recreate availability. Then, at 60 days out is something called Breakage. At that point, Disney can take the rooms that DVC Members have not yet booked and make them available to the public.
So, if in the initial chunk [once everything gets loaded, which can take days or even weeks] your preferred room type is not available, checking back again sometimes you will get lucky and new availability will happen with that room type in the months leading up to your stay.
Finally, if you take a look NOW for your preferred resort(s) and villa types for next May, June, July, and August (and then into Sept) and then keep checking regularly with rolling forward dates, you will get a sense of the pattern of when they load for your resort/room type. Keep in mind that it is a small snapshot in time and it could be influenced by covid. But you will get to see as they load them, how they are loading. And you should get some advance warning as they are getting close to your preferred dates that they are likely to load them soon as you will have seen the earlier dates loading in.
So for example, right now via the Canadian site the only villa stay one can book for June 25-28 2021 is at Riveria. But for June 21-23 most have at least some availability (not at either AK or BC), and if you go back further to June 7-9 everything but Jambo House has availability. As you can see, not everything loads at the same time.
Good luck.
SW