This question has kinda been a stumbling block for me since I had found a previous explanation (that wasn't clear to me at all) but both my own understanding/thinking and this thread has led me to believe the HSC just made a mistake (it seems weird though for them to make a mistake, for quite an easy question IMO)? The only explanation I had for it which I mentioned before (and which actually doesn't make much sense) is from here: https://www.youtube.com/watch?v=KM1XFOCzKDE
This is an HSC teacher I think so I'm not sure still? Haha general consensus on BoS is that its wrong, but this guy seems to have justified it somehow, but I'm not too sure. If someone could clear it up for me once and for all that'd be great!