The current Mathematics Advanced syllabus was
endorsed in 2017, meaning that 2017 still fell under the old syllabus, back when Mathematics Advanced was called just Mathematics. The current syllabus was implemented for year 11 in 2019 and year 12 in 2020, meaning that the 2018 and 2019 Mathematics HSC exams were designed to assess students according to the previous syllabus.
I hope this helps!