I don't think a typo depends on proximity of right and wrong keys. The last word of this definition seems to fit:


- Free On-line Dictionary of Computing (26 May 2007) :

typographical error
typo

    (typo) An error while inputting text via keyboard, made
    despite the fact that the user knows exactly what to type in.
    This usually results from the operator's inexperience at
    keyboarding, rushing, not paying attention, or carelessness.

But I'd still argue that reduced dexterity can lead to carelessness.