But lots of things are legal or not based on what typical people would do or think. "Battery" is contact a normal person would find offensive. So touching someone's shoulder to get their attention is not battery, but poking someone in the rib might be. More relevantly, implied licenses to access property are defined by reference to what a normal person would consider implied. So an invitation to enter a store implies a license to access the parts a normal person would assume they can access, and not parts a normal person would assume they are not supposed to access.
It's not a technical shell game. If you asked your mom, "hey, do you think they meant to have people be able to access those documents, where you can only get to them by editing numbers in the URL," she would say "no." That's what defines what is legal or not in this context.