I had about 1,500 hrs on the bent tailed Whirlwind, a jet propelled version, and the perils of aft cyclic was only mentioned during landing. On lift off when the collective is applied even with progressively aft cyclic the coning angle increase will compensate for the rotary star movement. All the time I was on them, 6 years, I never knew of an accident involving the chopping of the tail boom caused by pilot error.
I would guess the above accident is a result of an overpitch on arrival at the helipad so it landed heavily on the rear of the pontoons.