fwiw i lost use of my right hand for a few months (it's largely ok now) and it made surprisingly little difference to productivity. i don't think anyone else noticed! turns out i spent more time thinking and less writing than i had assumed.
I've often thought this was the case, but fortunately haven't had an opportunity to test out the theory. Occasionally I've seen software development jobs where they look for the ability to type some number of words per minute. I think that is a red flag.