1.6 Rocker Arms for /6

this is what I found from a hotrod article I found I've been doing research all day on this matter

it shows that the difference between the ratio is the length of the valve stem side which in my mind is to open the valve to its fullest right or wrong if my thinking is wrong
now if a builder were to mill the head lets say. .080 wouldn't that change the geometry of the valve train making the push rod .080 of a inch longer which would in turn would open that valve that much farther
please correct me if I'm wrong
aaron