The ATSB report was a crock. One of my favourite failings of the report was that they changed the radio transcript between the draft and final report. Another is that they used groundspeed (from radar returns) plus the forecast wind to estimate airspeed. But, they used made the same adjustment both flying away from Bankstown and returning to Bankstown. I forget the wind direction, but they (for example) gave it a headwind in both directions. Then they used this flawed arithmetic to criticise the pilots airspeed control!!
Its not at all clear that the pilot shut down the wrong engine. The engine he left operating was still operating, but failed to allow the aircraft to maintain altitude. It was never investigated whether the operating engine was capable of producing full power.
A factor that was never highlighted in the report is that the pilot complied with ATC descent requests. These descent requests were the standard profile that ATC use for its own convenience to descent IFR aircraft below the Sydney steps. So, the pilot did not find out that the aircraft would not maintain altitude until it was too late and his fate was sealed. For me a massive lesson is that ATC are not necessarily going to have your best interests at heart in an emergency. If the pilot had refused to comply with the ATC descent requests and maintained altitude, there would have been a happier outcome.