Crab:
The teetering range is not the same as the flapping range as the hinges are separate and mostly independent of each other.
Crab, not sure if you quite realize how the Robby head works, apologies if I just misunderstood you.
Teetering and flapping are indeed the same thing on the Robby. The center hinge is the flapping hinge. The outer two hinges are coning hinges and perform the same function as blade bending in the Bell. It is possible to mis-rig a Robinson to flap around the coning hinges, but (I'm told) it flies really badly and you would know something was wrong with the rigging. Basically you set the friction of the hinges by the shim stack-up... part of the rigging (besides measuring the friction force with a special tool) is to check that when you lift the blades the blades move around the coning hinge: "Check coning hinge friction by lifting blades until spindle tusks clear droop stops. Hold one blade level and cone opposite blade. Rotor hub may not teeter as blade is coned. Repeat check on opposite blade".
There is 12° of flapping authority on the Robinson head.
The head design is indeed unique and patented by Robinson. Using coning hinges instead of a thicker/heavier blade kept the R22 weight low. Keep in mind that at the time, with only a 150 hp engine, Robinson was concerned with saving ounces, let alone pounds.
I've been teaching in Robby's for 30 years and have a great deal of respect for the people who produce them. I do think that the R44 is a better trainer than the R22, however there is a large part of the student population that doesn't seem willing to pay an extra $100/hr for the larger machine. Anyone who thinks it's a cute little trainer is crazy. It's a fun machine to fly, but it's nimble to a fault with not nearly enough inertia for low time pilots, IMHO, and it can bite hard if you don't know what you're doing. The R44 has much higher inertia and lots more available power in a training environment and I think makes a much better trainer than the R22 (but again, money). I learned flying R22s and it was a real financial stretch for me, so I totally understand people going for the absolute cheapest solution they can find.
I personally would welcome a different design head given the large number of inexperienced pilots who fly the Robinson. Of course, every head design has it's limitations, but eliminating the low gee issue probably makes sense.