In the original story, the teller did not precisely follow the "document's" instructions. The script he was supposed to run would generate codes that he was supposed to use. In stead he used codes typed into the "document." I would bet the teller actually read the script and, rather than waste a chance to know more about the system, simply "tried to follow the logic" of the script. He would learn about the system doing by hand the tasks in the script. But, presumably, he did not think through the privileges that the script would need to set up his account. Or worse, he did (as an amateur, would-be BOFH), but had not properly counted on the laziness of upper levels, or anticipated the linkage to the production system, which should not have existed.