The main part of the confusion on this subject is that Celebrity has not updated their web site to match the current dining options when booked in a AQ cabin.
Just remember (until they update their web site, if they ever do), select "traditional", with a preferred time slot, and you will be assigned to Blu. When you get on board, you can dine anytime you want. We went early because 1) we eat early at home, and 2) it was great having a table by the window every evening.
BTW - - Even though we were at our table by 6PM, it usually took between 1 and 1 1/2 hours for dinner. Not rushed at all.