Thanks wrench1 (#332) for explaining tail rotor drive components and their arrangement. On the basis the L-3 drawing remains representative of an L-4 in terms of overall layout, I added abbreviated labels pointing towards the items you described (hopefully correctly).
As with TwinHueyMan (#333) and JamesT73J, I certainly see the similarities between both tail boom failures, only that one managed to "hang on".
Returning to post #259 by SansAnhedral where the missing tip of one rotor blade was sketched onto the photo of the recovered rotor, I was wondering if there was any evidence of that part already being missing off the main rotor on its way down. If you view from 0:46 in the following clip, you could certainly convince youself a portion was already missing in the air:
To illustrate, a screen shot from that video:
So question then is whether the missing 'tip' was the 'first' failure (causing substantial unbalance in rotor with 1 per rev vibration), or did the tip only fail after striking tail boom due to a substantial rotor 'hop' or deflection or as tail boom parted? In post #329 Bell_ringer reports seeing the tail boom passing through main rotors, but on the videos I have come across, the helicopter is too grainy to make out much at that point. Is there a clearer clip somewhere zoomed into the helicopter?