Everything else being equal, typing speed will help you try out stuff faster.
Language might make a difference there. Writing C# with a QWERTY keyboard, you still have to interrupt a normal typing flow for your parentheses, braces, etc.
I suppose it's helpful if you're writing long comments, but for the most part, I rarely hit sustained bursts of my peak typing speed when writing code.
To be controversial, a language that rewards typing speed seems to me like a failure of tooling, why am I manipulating text like a caveman (ok.. ok.. Mesopotamian) rather than with the symbols that the language actually deals with.
It helps a lot with most programming languages. Snippets for if, while, and for can also help with the {}.
Of course your senior engineer that wrote the thing will be more productive than your intern that writes 1000 WPM.
I am pretty sure that people who didn't learn to type properly have to switch their whole mind frame from the content into the typing, back and forth.
Some people even speak outloud, or at least move their lips according to, whatever they are typing.