Yes, they are achieving this through the introduction of more theory questions, rather than differentiating students on how well they can manipulate numbers. As I said, the theory questions always seem to be answered poorly and at this stage make a good platform for separating students. Over time though, students will become accustomed to both theory and arithmetic questions and VCAA will have to work out some other way of keeping things reasonable (perhaps reverting back to the to only two Maths subjects rule is a possible solution). I'm not sure making the questions more difficult would really work, because once you leave the 40-50 range, the cohort really starts to dwindle down in ability.
That being said, this year's Exam 2 cutoff was higher than in previous years, so perhaps students are already grasping the theory very well considering much of the exam asked for a worded response.