For Business Studies, year 11 content is not directly tested in any year 12 assessments (including the HSC exam). For example, you won't be assessed on the classical approach to management (which is a Preliminary concept that is part of the Business management topic) in year 12. Instead, you will be assessed based on your knowledge of the HSC syllabus as well as other requirements of the HSC course, such as the effective incorporation of case study material in your Section IV responses. For example, an assessable component of the HSC course in year 12 would be the elements of the promotional mix, which is a concept within the HSC course that is part of the Marketing topic.
I like to compare the Business Studies Preliminary course to the concept of assumed knowledge that is relevant at university. It is definitely useful to remember the main concepts taught within the Preliminary course, but the focus should ultimately be on the HSC course (because that is the assessable component). The importance of the Preliminary course lies in the fact that it provides foundational knowledge of the most basic business concepts, which you must have if you wish to progress through the HSC course in an effective manner, allowing you to achieve marks. For example, it would be assumed that as you commence the HSC course, that you know what "management' means. The HSC course covers more specific concepts with respect to each of its topics, while the Preliminary course provides you with the basic knowledge of the main business concepts that will allow you to learn and effectively manipulate HSC content.
I hope this helps!