If you're renting, then it's on the owner to worry about what time they need to be online. The time when booking opens for the 11-month window does not affect the rental agency websites.
FWIW, August is not a high-demand DVC period so getting any grand villa should be easy at 11-7 months. It's only an issue for those which are in limited number and require few points (i.e. BWV and OKW GVs).
ETA: Also at issue is the availability of an owner at your preferred resort with sufficient points available to rent.