Some contributors have disregarded the main point made by the OP. After all ATSB, did not question the flyability or otherwise of this particular STAR.
It was more a question of why the captain did not promptly stop the automatic pilot placing the aircraft further into the steep angle of descent to the degree that it did. By the time he took action the autopilot had already done the dirty on him and the aircraft was very low on final.
The reluctance of crews to disengage the automatic pilot and revert to manual flight to correct an undesirable flight path is a re-occurring factor frequently noted by flight safety researchers into the subject of automation dependency.
However, continuous use of autoflight systems could lead to degradation of the pilot’s ability to quickly recover the aircraft from an undesired state.
A case in point?