These are totally different versions of the concept of "literacy", though. Being able to read/write abbreviations of "eggs, scrambled", or "oatmeal" falls well below sixth-grade reading level. Literacy statistics involve much more comprehension than reading/writing food orders. Plenty of illiterate people do work in restaurants writing food orders. This is just a systemized way to remember orders, one that is used across all Waffle Houses, so that an employee from one restaurant switching to another will be just as effective, with no cross training or cultural difference.