In my opinion, there are some really, really small correlations between a typing machine and a piano.
Main difference is that typing depends purely on hand dexterity, whereas playing piano involves way more horizontal movement including arm and shoulder activity. You don't even have to move your hand position on the keyboard, on a piano you're always moving from left to right. I do not think (who knows, I'm wrong, just my thoughts) typing helps playing piano at all, they differ too much.
If it would help anything at all, then it would be purely technical (not involving essentials such as fingering, theory, reading music, etc). It might improve feeling and touch of 'keys' even though they differ a lot in size. Perhaps for people who never use this part of the brain that involves small locomotion skills (finger movement) and localizing keys blindly, typing might benefit playing piano. I can't tell from experience, Ive typed blind since I was 12.