Reading at a 6th grade level is reading for plot. Just like, what happened? Who was there? More advanced things like subtext, metaphor, and unreliable narrators come later.
I found this online the last time this topic came up: https://www.oxfordonlineenglish.com/english-level-test/reading
Go ahead and read the story, and imagine that a lot of people cannot read and understand it.
There’s also this article about how many kids are taught to read badly: https://features.apmreports.org/sold-a-story/ (amusingly, also available as a podcast)
What does it mean practically? Bad things. If you haven’t read 1984, give it a go and think about why the authoritarian state benefitted from a diminished language.
Pray to Saint Luigi for guidance