I'm not sure about the overall argument.. But I think arthritis of the fingers manifests eventually for most people who work with their hands and finger movement combined with any compression on tendons exacerbates carpal tunnel syndrome. Ergonomic I/O makers are essentially experimenting on the population, but less ethically as their bias is in using a bunch of nonsense to further a dialogue that supports whichever patents they obtained.

Personally I don't believe anything requiring 3 hands could be adequately tested given the freedom of movement given to the subject. I think only 2 hand home row keyboard use with specific additional positioning requirements has a flake of scientific rigour. (This is why I could only honestly support the track pointer in the home row as the least risky of the choices as it is the smallest deviation from something with a foundation.)