When the Board publishes its marking guidelines and notes from the marking centre, the "student outcome"
chainsaw: ) that was tested to that particular subquestion will be written next to the subquestion. The Examination Committee are obliged to do this to ensure that a 2U student could, feasibly, get 100% in the paper.
Even so, there was nothing in the paper that required 3U knowledge. Even if there were some skills that were perhaps outside the syllabus, we should be thankful that the Board is producing examinations with a bit of creativity.
Would you prefer it if we merely were given a set of 1000 questions to memorize for those would be the only questions the exam committee could set?
Mathematics is one of the few HSC examinations that have (some) creativity in their composition. They're not the most creative; but at least they're not banally predictable.