It's not that fast typist is an indicator of a good developer, but a slow typist is an indicator of someone who hasn't spent a whole lot of time in front of a keyboard.
Or they have some motor disabilities in their arm/hand, which you should check for before making a judgement. Some people have carpal tunnel, some people have tremors, some people might have other condition they might not have even know themselves or would like to talk about openly.
