Scifi wrote "...It will lose more lift than the Mainplane, and because of its moment-arm, will make the rear of the aircraft drop... This will cause a higher nose-up attitude, and is what creates the aircraft's pitch stability."
What you've described is pitch instability, not stability. If it was pitch-stable, the aircraft attitude would remain the same. What the reaction you describe will do though is to maintain a more stable AOA - protecting from stall during a disturbance.
I hope at least that we've established that a wing does experience a decrease in AOA when entering a downdraft. Otherwise we would experience lift in this situation (assuming we're not approaching stall)- which for me defies all experience and logic.