Is the tendency during the gust (constant speed) to start to recover to level, but this will be achieved fully once gust is removed? Maybe there is no such thing as a gust where speed remains constant??
I really don't know much about stability, but my take on this is:
Let's assume a sharp-edged gust of constant velocity. When an airplane in steady level flight encounters an upward gust, the angle of attack increases. As the angle of attack increases, the lift increases, and when the lift is greater than the weight the airplane will be accelerated upwards at initially the same speed and pitch attitude. A stable airplane tends to return to the angle of attack it is trimmed at, so the airplane will tend to pitch down to regain the initial angle of attack. However, that tendency is not very strong but the angle of attack decreases mainly because the vertical speed increases. When the airplane vertical speed is equal to the gust velocity, the airplane continues to climb, at the trimmed angle of attack and speed, at the same pitch attitude as it had initially in level flight. When leaving the gust the airplane goes through a similar, but reversed sequence but its final altitude will be greater than where it started, by an amount of approximately the gust velocity times the time to traverse it.