I think you're right. I'll add on: there's a lot of thinking that does not need writing, and there's a lot of writing that needs no thinking. Deng Xiaoping and other greats wrote pretty minimally for their own thinking, if at all. Whereas many of us not-so-greats seem to knee-jerk comment without a single thought.

It makes sense for our age. Amid a thousand distractions, typing on the keyboard gives the illusion of getting a grip. Note-taking on my computer gives the illusion of a second brain. Ululating on the internet gives the illusion of sharing thoughts.

Instead of "writing is thinking", I prefer "thought precedes speech" https://inframethodology.cbs.dk/?p=1127; it fits the small human mind better though I've yet to learn it properly.