Donald Knuth used to go to a secretary school to learn touch typing, and IIRC he could easily type more than 120 WPM. Yet he decided to write his books and papers first with pencil and a piece of paper, and then type them out. The reason is that he found that he typed faster than he could think, which in turn interfered with his thinking process, while writing on paper matches his speed of thinking.

I also find taking notes on paper helps me focus more than typing, but it could be just that writing slows me down so I have more time to unconsciously reflect more. I also find writing math on paper is way more effective than using a computer, but that's most likely because I'm not that familiar with LaTex, so typing out equations interrupts my thought process.

I read somewhere that he even programs on paper and punches it into a computer when he's done.

As for myself, I definitely understand the problem he's describing. I catch all my fleeting thoughts with a keyboard, but I always find my mind wandering into tangents and end up losing the focus of what I'm really getting at, or I end up in a cycle of endless micro revisions. When I started writing with pen and paper it enforced a certain economy into my writing process. By having a natural speed limiter, I have to focus more on the heart of what I'm getting at; being in the zone writing with pen and paper feels totally different to me than writing on a keyboard, you get into a much deeper state of focus.

I have always had the opposite problem.

In grade school had to go to all these classes during recess to get different pencils, pens, grips, wiring methods.

The reason was my hand could not keep up with my thoughts. So the result was skipped words, and merging of two words and all these other things.

I am still poor at spelling, but the solution was typing. Once I started typing well my grades went up and I no longer found doing the work a chore.

Maybe it was different when I was a kid, but nowadays writing anything more than a signature with a pencil or pen makes my fingers tired and crampy.