Well written Paul !
Over the years I had 3 governor failures (3 different companies) and it's not a big deal. Turn off the gov switch and continue flight, operating the throttle manualy. This is part of the PPL(H) training and should be well understood by any student. Of all the emergencies you train for, gov failure is probably the one that you might have one day.
Regarding the topic: why do you call this a gov failure?? in the german text I can read "er einen Leistungsverlust gehabt" which is a power loss. Lycoming engines are very reliable so an engine failure is highly unlikely, fuel starvation or low fuel with a high angle of bank turn? On final approach you can have vortex ring... The R44 turned due to a plane departing, in the turn you loose lift, rate of descend increases, if the turn was 180 degrees then they had wind from behind etc. Or maybe they ran out of power (slow speed, out of ground effect) and overpitched, unlikely with 3 pob in a R44 unless very heavy pax and lots of fuel.
So there are many possibilities for this crash but I don't think the governor is to blame. If it was the governor, the pilot should have known what to do about it. If suspected malfunctioning, turn it off. So don't do like in the atsb report that was also linked on the top, the pilot left the switch on and operated the throttle manualy. This can result in the pilot giving an input on the throttle and if not held properly, the governor might also give an input, risking an overspeed or low Rrpm (losing lift). Read the POH including the safety notices and follow it. Learn from the mistakes that others made.....