The year that decides which subjects you are allowed to take
Grade 9 is the last year of the Senior Phase, and the November results are what a school uses to decide which FET subjects a learner may take in Grade 10. A learner who wants Pure Mathematics, Physical Sciences or Accounting generally has to show the marks for it here first.
That makes Grade 9 unusual. No university will ever see these marks, but they quietly set a ceiling on what a learner can study for the next three years, and on which degrees are still open at the end of it.
Past papers are the cheapest honest measurement available. A learner who scores 42 percent on a real Grade 9 Mathematics paper in April knows exactly what has to change before November, and April is a much better time to find that out than December.