Wait a minute. A typist is going off pure memory, finger key placement. That has nothing to do with examining individual signatures. A typist does not even look at, nor examine the keys during the typing process. Where did you come up with this??
The one on the right is fiddling with the mouse and swooshing her hair with her hand. The one on the left is concentrating...one hand on the mouse and one on the keyboard. What a difference a professional can make.