I have just posted a question about HSK characters list not matching the most common characters list, but I think this question here is a bit different.
I also wonder why do HSK tests have so many words on them that do not appear on any of the level lists (like a 呗 that I saw on an HSK 5 and it's not even at the level 6 list) or words that do appear in a given level, but are advanced compared to the level they appear (like a 公共汽车 appearing on level 1 even if it's only a level 2 word).
1. Why don't the people that prepare the exams follow their own lists?
2. How should a student study for HSK with such a chaotic list situation?