Is it possible to be a productive programmer with slow typing speed? Yes. I have met some.

But…can fast typing speed be an advantage for most people? Yes!

Like you said, once you come up with an idea it can be a huge advantage to be able to type out that idea quickly to try it out before your mind wanders.

But also, I use typing for so many others things: writing Slack messages and emails. Writing responses to bug tickets. Writing new tickets. Documentation. Search queries.

The faster I type, the faster I can do those things. Also, the more I’m incentivized to do it. It’s no big deal to file a big report for something I discovered along the way because I can type it up in 30 seconds. Someone else who’s slow at typing might not bother because it’d take too long.