In the 1968 "Mother of All Demos" , Doug Engelbart demonstrated several cutting edge technologies. They were still decades away from mass adoption, but in this video he demonstrated: computer networks, video conferencing, shared editing of a digital document and the computer mouse.
If you blinked, you might have missed one particular user interface device: a Chorded Keyboard . Chorded keyboards were not new, though Engelbart might have been one of the first people to use them with a digital computer.
If you look at a video of the demo , you can see Engelbart use the one-hand chorded keyboard at around the one minute mark. It's interesting to note it's only used while his other hand is on the mouse.
In this demo, at least, Engelbart seems to think of the mouse and the chorded keyboard as a pair of components that make up the same computer-human interface. That's a distinction that may have been lost on modern computer users.
There's no right or wrong way to use your computer, really. If it works, then it's probably "right." But the chorded demo page is intended to give people an easy way to test out one handed typing, just to see what it's like.