You might need to look around more. The wikipedia article shows 'c' on the middle finger, like I was taught. I can't imagine doing it with the first finger, but I suppose it just depends on how you were taught.

Looking around, I can't even FIND a "c on first finger" fingering.

- https://en.wikipedia.org/wiki/Touch_typing#/media/File:Finge...

- http://www.typingme.com/touch-typing/typing-lesson-9.php

- https://agilefingers.com/articles/touch-typing-finger-placem...

- https://www.computerhope.com/issues/ch001346.htm

- https://www.ratatype.com/learn/

and on and on.

I did watch me and my friends' touch typing behavior, and most of us use left index finger for RFCVGT(B), and right index finger for YUHJ(B)NM. the character in parenthesis means it overlaps between right and left area

That's what I do. I'm clearly wrong about the fingering charts though (I learned from an ancient DOS program, so I can't check that one). I have a picture of a symmetrical one in my head; C is the equivalent of M, so it seems like they should use the same finger.

Didn't even realize I use index finger for c until you mentioned it. Turns out I should be using my E/middle finger. Hm.