I don’t think knowing hanzi helps. Simple Japanese words for example 凄い　強い　走る, the pronunciations of them are completely different from Chinese and they are what you need to know to pass the exam. Advanced words have simular pronunciations to Chinese but they don’t often appear in exams. And Chinese see a japanese word wriiten in kanji they will think “oh I can understand it!” so he left without remembering its pronunciation. When Chinese see “走” in Japanese they may think it’s “walk” because this hanzi in chinese means “walk” but in fact 走 in japanese means run. So knowing hanzi is sometimes even a trouble