The GCSE listening paper sounds strange because the Edexcel board paper is designed for both Cantonese or Mandarin in a single paper for the candidate to choose the language option. Therefore the questions are mainly written in Mandarin and directly pronounced in Cantonese and hence some phrases are not the usual Cantonese dialect😅
Looks like this tests the comprehensive capability of the students but these exams seem to have been prepared by those English speaking people who learnt Cantonese in southern part of China. You know Hong Kong Cantonese is slightly different, like American and British English - the way they are spoken and the word usage, and so we should accommodate these differences.