I asked my English Language teacher to have a look at the 2017 examiner's report AC too, and she said that she when exam marking would not at all have marked this high, and that she thinks it sits more at a high-medium level. A few more things about your question that'll be helpful - 'contextual factors' include importantly a discussion of register, which the first two body paragraphs do cover. Context is primarily intended to be covered in the introduction paragraph. This is the purpose of writing an introduction for an AC, and why you have a list of things to cover (which differs from school to school). Context in this text I would consider well-covered. What is lacking is metalanguage - you should have at least three metalanguage points in your AC not three metalanguage terms; describing a feature as jargon in the semantic field of real estate is still only one point, so the 2017 AC lacks substantially here. Elaboration and discussion of examples and purpose is not deep or enough to at the very high end but it is concise and does the job. Hope this helps. I'm only doing lang this year too so what I say is just my understanding of it.