Something I realized, but did not announce to my friends out of embarrassment of it having taken me this long to understand, is that non-fiction writing uses figurative language too. Obviously I knew it did. But I didn't know that some ideas that seem like the author wants them taken literally, aren't what the author means.
Note: I don't mean that I discovered that we aren't supposed to be eating babies. I mean that people do it with points that sound reasonable, too. (sorry to any baby-eaters in the audience.)
An example: a few weeks ago, I read an old book about cats. I don't know exactly how old it is, but somewhere in the ballpark of 20-40 years. Anyway, the way the author talked about cats stuck out to me in how happy and upbeat it was. Were all these compliments true? Not really, but the author engaged with the core idea of cats being cool very well. When I mentioned figurative language, I meant the exaggeration of position, not the regular kind of figurative language. Regular figurative language is useful in expressing one's exaggerated position. It is not the exaggerated position.
Another example: in How to Take Smart Notes, the author repeatedly focuses on how only writing is thinking. Which is a stronger version of the truth. Sure, I need to write things down to remember them, and the system he presents of bottom-up writing is great, but I can think in lots of other ways. I schedule time into my week to go outside and sit in a tree while thinking. (This kind of thinking tends to be more about changing my mindsets on certain ideas than producing professional essays, but it's still thinking.) It's not that he's somehow missed this, or defined thinking in such a way that his argument is already won. He has presented an exaggerated idea in order to make it stick in people's minds better.
It doesn't really matter if either author actually meant what they wrote. It's kind of like how I always know when a comment is sarcastic. I'm not good at it, I'm just good at being certain. I'm not even sure my categories of funny line up with society's. But again: it does not matter. It doesn't have to be true, it just has to be useful.