When deciding whether to study Chinese, students often state two goals: (a) to pass a HSK test, and (b) to read Chinese news articles. I'm towards the end of HSK5, and I already read some news-related opinion pieces, particularly those concerning COVID-19.
For concreteness, yesterday I read an opinion piece 澳大利亚“大义灭亲”, and I mostly understood it without much help. If we put aside non-HSK terms like some idioms [e.g. 大义灭亲 ("righteousness before family")], people names [e.g. 莫里森 (Morrison)], place names [e.g. 维多利亚州 (Victoria)], etc., the words I didn't understand were:
HSK5: 分布 ("to distribute"), 敏感 ("sensitive");
HSK6: 蔓延 ("to extend"), 步伐 ("pace"), 演变 ("to evolve"), 截至 ("up to"), 陷入 ("sink into"), 一系列 ("a series of");
Non-HSK: 矛头 ("to spearhead"), 恰恰 ("exactly"), 不光 ("not only"), 变异 ("variation"), 分化 ("to split apart"), 实时 ("real time"), 统计 ("statistics"), 援引 ("to quote"), 亲口 ("one's own mouth"), 质疑 ("call into question"), 毒株 ("virus strain"), 疑点 ("point of doubt"), 热衷 ("to feel strongly about"), 追随 ("to follow"), 联邦 ("federal");
Non-HSK: some four-character sayings like 追根溯源 ("trace back to origins"), 视而不见 ("turn a blind eye"), 鹦鹉学舌 ("to parrot [what someone says]"), 置若罔闻 ("turn a deaf ear");
Non-HSK: 选边站队 (something like "choose to sideline your team").
Thus I'm getting the impression that spending a large amount of time studying the HSK6 vocabulary would not be particularly useful for reading Chinese articles. (Online estimates for the HSK6 study time range from 1000 to 2500 hours.)
Question: How additionally useful is HSK6 over HSK5 for reading Chinese native news and opinion pieces?
I'd prefer academic answers, if possible. However, I did a basic search for relevant papers, and found nothing relevant.
I'm aware of a web article HSK 6 gets you halfway which emphasizes how HSK6 is not enough to get a student reading smoothly, but it doesn't answer how additionally beneficial HSK6 is over HSK5.
For another data point, I went through a totally different article about celebrity 金星, where I encountered these unfamiliar words:
HSK6 (10): 家喻户晓, 编织, 感慨, 潜移默化, 靠拢, 特意, 罕见, 争议, 认可, 任命
non-HSK (26): 互动, 高调, 秀恩爱, 露背, 吸睛, 遮阳, 另类, 复古, 挽, 般配, 献上, 收养, 亲生, 长相, 挑, 血浓于水, 血缘关系, 饱受, 诋毁, 抨击, 这阵子, 实属, 现任, 轨迹, 找茬, 回怼
non-CC-CEDICT (6): 白养, 同框照, 味十足, 油纸伞, 信命, 热映