1A & B are still blocked due to weight and balance issues. I recently lost 1B on some flights that were changed or canceled and had to settle for 2D. For me it is a leg room issue, and as a MVPG, we used to be able to get 1 A & B. For me it is just another reason to avoid Horizon flights unless there is no way around it.
I will still ask for 1B or 1A at the airport as the seats are under control of the gate agent.