I have experienced an engine failure in the type aircraft and had no problem maintaining height for a considerable distance, over 60 NM.
Exactly! So what happened here then?
The whole ATC instructions may be nothing but a misdirection in analysing this. Maybe it didn't help, but seems very possible it was not the root cause of why the aircraft could not maintain height.
The analysis of the power plants was skimpy, to put it politely. Who does the ATSB use to look into these engines? An overhaul shop, experienced piston engine expert, or a staff member that once took his lawnmower apart and then got it going again.