The SDTS standard assumes that the conversion from the world to the database is not particularly problematical. Accuracy can be simply tested when a test translates directly to the database. What they mean is not the Real World in all its complexity, but the world as seen through a particular approach, a particular set of rules. This concept clarifies how all tests are performed. They observe through a particular lens, a particular point of reference.
Many geographic phenomena have indistinct boundaries or have complex attributes.
Testing a fuzzy object using sharp rules may give silly answers. This isn't getting any easier.