Entering and flying through a downdraft is NOT a single event with a single effect and control response. It is a dynamic situation.
Since the event sequence will START with a stable airplane entering the downdraft, the AOA will temporarily decrease due to the wind vector. However, an almost-immediate control response will be made, pitching up to regain/maintain altitude, INCREASING the AOA. Until the engines compensate, the airplane will then be slower than in the stable state. While the downdraft persists, the pitch attitude will be higher, since the airplane will be effectively climbing.