CASA have never designed instrument approach procedures. It has always been an Airservices Australia task or the task of a CASR Part 173 Certificate holder.
I was told that in the mid 90's the function did indeed transfer to the then newly minted CASA from the CAA (part of DASR?), although the people involved didn't physically move. The function was later transferred back to Airservices. CASRs didn't come in till the late 90's, so maybe that's when.
Anyway, minor point.
CASA tend to not produce their safety assessments/cases to explain a directive - they are the Regulator, of course
