Don't confuse a nose down attitude with a negative pitch angle.
Hard to do, since they are the same...
Pitch angle is relative to the aircraft longitudinal axis; so is "nose down attitude."
Wing angle of incidence (and thus the AoA) of a clean wing may vary slightly so that the fuselage is at the lowest drag angle in normal cruise.
Extension of flaps may significantly increase the effective camber, angle of incidence, and AoA of the wing with a constant pitch angle.