If there was only two students in the course.
There algined exams marks would be each others internal assessment marks. (seeing as first and last.)
Eg. Internal External
Stuednt A 80 70
Student B 75 95
marks would be (internal/external/final)
Student A 95/70/ 83
Student B 75/95/ 85
So that huge gap in the HSC exams wouldn't mean as much as the moderation would screw Person B over. Why ranking first is great.