In all fairness to the instructor, he was clearly caught by surprise when the student hauled back and apparently froze momentarily on the controls. This left the instructor in an unenvious situation so close to the ground.
When being grilled by investigators after the event it must have been difficult for the instructor to recall every single movement he made in his attempt to recover the situation. There was no mention by ATSB of the specifics taught by the operator of the flying school as to the stall recovery when a wing has dropped. Maybe ATSB never got around to asking because they didn't think it was important.
The OP brought up a relevant flight safety point when the instructor told ATSB that aircraft was prone to dropping the right wing during practice stalling. Was that the instructor's personal experience or had other instructors noted the same thing? By not discussing it further in their report, ATSB seemed to have brushed that off as inconsequential. Nor was mention made in the report as to why the aircraft was allowed to continue flying with that perceived defect and if in fact the defect was already reported in the maintenance release.