I never learned how to type "properly", i.e. "home-row" typing: my hands rest naturally somewhere between the middle and upper row at maybe 30° angles from the vertical, and some keys I strike with either hand depending on the word (e.g. t/y g/h b/n).
Yet I type faster than most people I know, and have had no RSI issues due to typing almost daily for 22 years. (I have had RSI issues due to using (gripping) a mouse; replacing the mouse with a trackball / no mouse eliminated this.)
This "nontraditional" method of typing leaves my wrists straighter and reduces repetitive motion, to which I credit my fortunate freedom from RSI.
The downside is that I am unable to use so-called "ergonomic" split keyboards, as my fingers are trained to work both sides of the keyboard.
(And I say "ergonomic" in quotes, because while most "ergonomic" keyboards, such as the Kinesis, are designed to reduce movement, my personal experience is that ergonomics is all about making more varied movement.)