Typing fast doesn't make you a good programmer though good programmers usually type fast. The only conclusion you can draw is that if you see someone typing horribly slow you can probably treat it as a warning sign.

Analogously, the same could be said about a lot of things.

I don't know how much of it is about good programmers wanting to communicate their thoughts faster to the computer and how much is it about good programmers having written so ridiculously lot of code since their childhood that they just kind of get bizarre typing speed as a side-effect, but it's definitely both.