My guess is that the 2 bladed rotor on the original 222 is of the family that has a significant "bounce mode" where the natural frequency of the collective pitch system (mainly in the rotor head) is very low, and naturally tunes to the pilot's arm/hand frequency.
Nick,
If that was true then why did Bell use a standard collective installation for the co-pilot's stick's on both the 222/230/430 and 214ST? If it was so problematic, wouldn't the co-pilot suffer from the same issue? I've flown the 222 from the left seat and never had a bounce problem.
BTW, there is a collective collet where the friction is set on the mast.
Chuck