Narrowing in
Flapback is what happens if the pilot does not relocate the cyclic stick to counter Dissymetry of Lift.
Flapping to equality is how the lift is kept equal around the disk if the pilot does not move the cyclic.
Flapback serves as feedback to inform the pilot that the stick must be moved.
Once the pilot has moved the stick to the correct place (running Dissymetry of Pitch) the Dissymetry of Lift has been cancelled and Flapback no longer occurs.
(Pleased to see this unconventional approach becoming common ground here now)
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A simple way to think about a rotor blade is that (almost) ANY effect that persists for a half cycle would cause a change of plane of rotation and need to be cancelled with asymmetric pitch probably from the cyclic stick.
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The matter of the Plane against which flapping is measured is again going to confuse the hell out of everyone.
Measuring flapping against the Control Orbit ( or Control Axis or Zero Pitch Plane) is utterly pointless and throws up incorrect statements (like "Max pitch is at the 9 o'clock" - not relative to the Zero Pitch Plane it isn't !)
I believe the most common definition of Flapping is concerned with how a blade would move around it's flapping hinge (if it has one).
The other useful definition of Flapping concerns the movement of the blade relative to the TPP - which is useful because it gives you an idea of how the plane of rotation will change - as in Flaback for instance.
Measuring Flapping against the Control Orbit has little practical use