I haven't been following most of this thread, so please take this as you like. If I'm rehashing someone's ideas, I apologise. My history; several decades earning my living as a pilot, mostly helicopter, military and civilian, small and large helicopters, North Sea for much of my career.
My hypothesis is excessive noise. There are times, even when chugging to the platforms/rigs and back, that my inadequate brain gets swamped by too much chatter happening simultaneously on the radios while my colleague and I are discussing operational matters. At times we might be forced to turn down one or both radios briefly. In other words "Aviate, Navigate, Communicate".
Yet I'm given to understand by other colleagues who have done those jobs, that police and EMS helicopter crews can be listening to four or more radios simultaneously, trying to prioritise which of the strident transmissions most deserves an immediate response.
So you can see where I'm going with this. In the extremely unlikely event that both engines should fail, a few valuable seconds could be lost before the pilot realises the seriousness of the situation and lowers the lever, after the rotor has decayed to below a recoverable rotational speed.