Boy I really struck a nerve with all of you.
let me offer a couple of precisions to maybe calm dowm the opnion.
1/ you would NEVER do that in flight, this was done in ground effect.
3/ as an aerospace engineer and a pilot I found it quite educative that the rotor can get any working aerodynamic efficiency at that speed AND that the engine has suficient torque at that regime.
4/ I understand well the negative mechanical implicatiion on the airframe, rotor head coning, engine, transmission and the AC was never to be flown again.
I would say with the nominal envelop and the maximum envelop possibly closer to each other in robinson products I always value out of the box data. The next low RRPM mighr be unexpected, believed to be unrecoverable or needed to reach the only autorotation spot so far out of reach.
with all that said: Good pilots know and respect the nominal envelop