Lu, you are trapped by your own words.
You state that all helicopters have some pitch coupling and you say...
"This is common to all helicopters and is called pitch coupling. Because of this coupling the pilot must make a correction in his cyclic stick position. "
But you already stated that the Robinson pilot is correcting for the unusual phase angle in the head.
So is the pilot now correcting for two problems?
I suggest the pilot does not make any corrections because the phase shift is cancelling the delta coupling effect.
The delta-3 or pitch coupling as you call it
was put in for the same reasons it is used in tail rotors- it limits the flapping angle and gives better rotor clearance at the fuselage.
Now as you say, pitch coupling requires that the pilot correct with cyclic.
I suggest that Robinson decided to put the "correction" in the controls and that is the purpose of the phase shift in the head. The pilot moves the stick normally abecause delta-3 coupling is automatically compensated for with the 18 degree swashplate phase offset from 90 degrees.
You also mention divergence of the rotor.
The Robinsom blade has twist like any other typical hekicopter. It also incorporates pitch-flap coupling like a tail rotor has.
Why should it be divergent? Are tail rotors dvergent? What is the design feature that you think is making this rotor divergent?
And where is the evidence that accidents are happening because of divergence?
By the way, the hinges are called coning hinges in the Pilot's handbook, p. 7-2 You call them flapping hinges and that is incorrect.
The the blades flap as a unit around the teetering pivot. The coning hinges allow for coning of the blades and that's why we don't call them flapping hinges. These are semi- rigid teetering rotors and not fully articulated.