crab is right,
the pitching motion is instantaneous, the horizontal bits may add to it but it is secondary,
the pitching of the disc, up or down, occurs whenever you raise or lower the collective or whenever you accellerate or decellerate the aircraft. a simple aerodynamic fact.
if you lower the collective and hold the cyclic position the nose will pitch down and the aircraft will accellerate, the nose will then pitch back up, flapback, and pass through its original position in a descelleration, this is static stability the nose will then pitch down and accellerate again, flapback, these up and down oscillations will increase to destruction if not controlled, dynamic instability.
flapback, the tendency of the disc to go back to where it was, occurs because of simple aerodynamics whenever you raise or lower the collective or accellerate or descellerate and don't compensate with cyclic.