I believe you are correct. It’s the pole’s accuracy in then nailing the chopper, right on the main rotor shaft, that seals the deal. That gearbox is scrap.
Not much sense putting a torque-limiting coupling in a tail rotor shaft, no matter how expensive the helicopter is.
As the main rotor chews further into the pole — or should I say the pole chews further into the rotor — a big chunk of one of the main rotor blades breaks off and flies directly into the tail rotor.
That's what causes the damage, although I still think there's a shock load failure of the main rotor shaft.