No HSC examination has included the case study in any other section other than in the extended response section.
Also, every HSC to date has given students an alternative (i.e. one question is a case study q, and the other isn't).
However if you are going to take the presumption that because of this you don't need to know a case study; be careful as you may have difficulties answering the other question. Its an insurance policy to know your case study.