There are at least two people who I'd dub "great hackers" who type essentially, two fingered. One of them suffers from horrible RSI (but, at one point, had the company hire someone to be their hands).
The other didn't grow up around computers/type writers (growing up in the 1940s/1950s in Soviet Union), didn't really heavily program until after graduate school and for the first decade mostly programmed by writing code on paper and having it punched onto cards.
Gah - when I was out of school, they could have paid me minimum wage and I'd be thrilled to take a job to be a great hacker's "hands." I can't imagine many better ways to see a master work.
There was a guy I worked with who was one of the most productive people on the team and a great coder. He could type fast, but not by touch - hunt and peck all the way. When he had his ergonomic evaluation, after seeing the way he typed, the evaluator recommended he try voice recognition software. He didn't.
I knew a guy who was wheelchair bound with no use of one hand and the other only semifunctional, able to peck out keys one at a time.
I can't claim he was a great hacker, but he managed to hold his own on the team and even outperformed some. If he can be competent with that level of impairment, I think it's got to be incorrect to claim all great hackers are great typists.
The other didn't grow up around computers/type writers (growing up in the 1940s/1950s in Soviet Union), didn't really heavily program until after graduate school and for the first decade mostly programmed by writing code on paper and having it punched onto cards.