I feel like I have also been alerted to Disney Visa resort deals/code discounts a week or so before open to general public. The benefit to this, I suppose is that only a certain number of rooms per resort is allotted to these deals so you may be more certain to getting the type of room you are looking for at your preferred resort for your dates.
I think I may have received an email and/or possibly a mailer from DisneyVISa. However, when I am booking (and even after I book as many here know, you can often retroactively have discounts applied and receive money back) I am often checking and rechecking Disney's site and DisneyVisa for "deals".