Also the community of fast typers would probably have started using MCCs if they are better.
Great point. Unlike, say, a Dvorak keyboard, nothing would have to have been replaced for production typists like me to add MCCs, but I never did it.
This stuff matters -- we are talking billions of dollars in productivity. But there is probably a difference between me, a visualizer with slow fingers, and more dexterous video-game-raised geeks. It would require that I be tracked as I move from 20 wpm to, say 40 on the Twiddler, to see if reverting to SCCs would then speed me up, or if my relative finger lag is permanent. I suspect that, given 40 years of putting out several thousand pages a week and never really exceeding about 55 wpm (I think), I am wired up differently. I also notice that I cannot reach easily for numbers and punctuation on a keyboard, but I can easily remember my weirdly-placed numbers on the Twiddler.
Maybe we should all have dueling MRI challenge matches.