This isn't' really true. In both survey systems the markings or pins or corners, etc only have meaning when combined with a legal document. In meets and bounds systems an 'x' carved into a fold of a tree, a burned wooden stake buried at a corner, an x on a rock are not warnings or visible signs of occupation. These are the exact opposite! These are pretty hidden and hard to see and only connect to each other when interpreted and found using a deed or legal document that describes them and their relationship to each other. It's no different in brand new developments today, the survey markers are buried and not meant to be seen. It's not a sign of occupation in any form, it's just a physical claim to land as described in a legal document.