I am always amazed at the use of angles to explain rotor dynamics. I find it confusing, and non-intuitive, frankly. Also, a quick flick of the wrist makes the cyclic change that angle vastly, and confuses the whole picture. Seldom is a flapping/lagging blade behaving like the diagrams, when the pilot is in the loop making control inputs. Also, the pristine logic of a teetering hinge head is a special case, any real rotor head has no ability to flap without making a roll or pitch moment input to the helo. For example, when we think that flapping relieves the differential lift, we are dead wrong, because that flapping also creates a large roll moment that the pilot must cancel with cyclic.
It is much easier to think of the delta velocity as the cause of a back-flap, (which is also the prime speed stability term for the rotor.) Increased speed makes the upwind blade a bit faster and the downwind blade a bit slower. This makes the rotor flap up due to phase angle, and usually roll slightly left. The extra pitch up requires the pilot to push the stick forward to put the nose back down, and this is perceived as a forward stick trim for increased speed. We call that Longitudinal Static Stability.
Backflap is the reason why you have a horizontal tail on all helos. If you didn't have one, there would be no way for the nose to stay down when a slight upgust hits the aircraft. The horizontal tail sees the nose up as an increase in its angle of attack, so it increases its lift, and presses the nose back down to help the pilot keep the aircraft from flipping. Without a horizontal tail (or with one that is too small) the backflap can make the helo very unstable in pitch, especially at high speed. In some helos, a big nose up can lead to loss of control, because the backflap is more powerful than full forward stick. This is usually a sign that the horizontal tail is too small, or the CG is too far aft (because the nose up is a combination of backflap and the net increase in lift applied forward of the CG, which also makes the nose kick up.)