Even if there is document to show that owners can book at 12 months, weeks often show up in II as much as 18 months ahead. Booking in MVC allows for 13 months ahead, which in no way affects owners being able to book at 12 months. You can look at it in terms of different inventories.
Since MVW controls all the moving pieces, they could pretty easily take a reservation that was, technically, a reservation for a reservation, with the official unit booking not occurring until a year prior. They probably can’t do this for inventory they don’t own or control (deeded weeks that have been sold) but could probably do so for inventory they own or control (unsold inventory, trust inventory, etc.)
I'm sure there is some mechanism they could use to abide by the deed requirements while also pre-booking reservations more than a year ahead. It could all be transparent to the user. Then at exactly one year prior to check in, some vast quantity of VOIs get automatically reserved by all those who had pre-reserved them prior. The poor slobs (US) who want to reserve those won’t stand a chance, though this might be a different bucket of inventory than we’d be able to access outside of DP anyway.
It all gets pretty confusing…