Always nice to see more stats especially if I can sort my courses/books according to it too. If data from that stas can be used to generate a readability score for material we import that will be useful. A score enhanced, based on words we already know.
There is a grammar site https://www.kwiziq.com/ that has a mind map system. Your analysis and visualization remind me of that.
I like you have a Harry Potter topic circle in your visualization. That is one of my goal to be able to read that book in my TL. Your visualization will show me how close I am to be able to read it. This can be motivating. Maybe if it can even recommend me books/material to read in my library in an efficient sequence to reach that goal that will be good.