No argument. I know the GPS's and landowner apps are not perfect. However, it gives you a leg up on the land owner making a stink as opposed to having nothing and then it's your word against their's.
Most of the time…and I mean a high percentage…of land owners have their property fenced (here in the west anyways). For them to change or hide their corner would require them to change the fence as well. They may need to get other landowners involved. Or…they may be moving their property/fence line onto Fed property. This is a lot of work most likely won't want to mess with. Getting LE and then possibly the courts involved, may expose their wrongdoings as well. I'm not saying it's not possible, but unlikely in most cases.