Do someone really needs to learn touch typing? It comes naturally when you are using computer daily.
i developed a pretty fast way of typing naturally, using 7 or 8 fingers.
unfortunately it caused wrist strain.
i could not use split ergonomic keyboards because some keys where "mapped" to the wrong hand for that.
i also could not simply learn "proper" touch typing on a qwert layout because my typing habit was too strong.
in the end i learned touch typing on dvorak to fix my wrist issue. maybe after 10 years i'll have unlearned qwert typing enough to go back? (not sure i would, i do prefer dvorak, it just feels silly to type at snail speed on others ppls keyboards).
Regarding speed - it didnt prevent to be TOP1 at university in typing contest :)
My naturally acquired typing style involves me holding my hands hands in just about the same angle as those "ergonomic" keyboards, but just using a regular keyboard. Fingers rest on LShift, A, W, D, and K, O, P, Ø with both thumbs on Space.
Should be noted that's on a "105-key" Nordic keyboard with US layout when not writing Norwegian, so the Ø becomes '.
For me this has worked quite fine for over 20 years. I haven't bothered measuring my typing speed because it's never the limiting factor.
So I simply asked her to teach me the proper technique and now, since decades already, I'm touch-typing the proper way.
Having said that: you can be very fast using improper touch-typing technique.
People can practice a skill for a long time, but if they don't focus on improving, they tend to just harden their existing habits.
However, it might be a good shortcut for people learning. I was taught at a youngish age to attempt to touch type (box over the keyboard and a tutor program) I fucking hated it, and I was slow, it was dull and painful.
However, Then I had a need for typing, so I got faster and faster, and the initial structure that I got from the rigid teaching, allowed me to learn faster than my peers.