nope.
To get a HSC mark of 100 - firstly get ranked 1st internally (doesn't matter what your mark is - just get 1st)
Secondly, get either 100% in the HSC exam (externals) or close to it e.g. one wrong.
Because of aligning, you don't necessarily have to obtain 100% in the exam, a 98% raw in the exam could align to 100 - depending on the subject.
Because you ranked 1st internally, the highest external mark will also become your assessment mark - so you will receive, 100/100 -> 100 HSC Mark.
e.g. I ranked 1st in Biology, then I did the exam and came first again with 96.. so both my assessment and exam mark were 96.