Perfectly formulated exposition on one of the advantages of writing. Don't get me wrong, I like to write anyway, but I too have found myself with a much better understanding of a topic once I've gone through the process of writing about it. Writing about something forces me to wrestle with it, to research parts about it and nail down in my mind how all the parts fit together. The net result of course is that I have much richer understanding of the topic than before I started to write about it.
http://thereformedbroker.com/2017/08/17/qotd-write/
Adding on to this thought, I remember reading in Erica Jong's seventies bestseller "Fear of Flying" about one of the protagonist's high school boyfriends who could just wind a piece of paper into a typewriter and pound out a multi-page paper on medieval history. No forethought, no editing, just straight through and done. While at the time I was pretty impressed with the massive amount of knowledge it would take to actually do this, in my maturity I'm actually thinking those papers weren't that good - undoubtedly the raw facts of that subject were there, but I just can't see how anyone could piece all of them together in a coherent form in one go. Good writing just doesn't work that way, and I am made to wonder if a strong, reflective writer like Jong wasn't making that statement too.