Yes, they often update the list depending on how booked, or not, they are. Sometimes it's very last minute. For example, there were no dates at all for July, and then right at the end of June they added about 15 days in July! Your best bet is to call and book, asking for your 15% off DIS board discount, or 20% if you're an AP holder. You could have backup reservations elsewhere for a rate you like better, if you want. Then if the Ent rate appears for your dates, call and get your reservation switched to the lower rate. If it doesn't, you can cancel and keep your reservations for elsewhere.
edit: I don't know, though-- early December is cast parties and candle light processional time, maybe that's why HoJo is thinking there might be higher attendance and isn't offering the Ent rate. For now, anyway.