My point is more that the people of the past weren't stupid; they didn't believe that a horizontal line couldn't be easily extended by a forger to hang over new

My point is more that the people of the past weren't stupid; they didn't believe that a horizontal line couldn't be easily extended by a forger to hang over newly added digits. Rather, our explanation today is lacking; there must have been some other reason for the practice. Or no reason other than that someone stated it and it become something that is always done that way.