But what were they thinking exposing the ordinal function, which returns an integer which is based on the order the enum values were in the file? You can change behavior by reformatting!
The claim in source is to have exposed it for use in EnumMap and EnumSet, two basically pointless data structures. They're so efficient! But their key is an enumeration so if to get big enough that efficiency matters means you will have enumerations with many thousands of members so efficiency is not your first problem. Or you are making millions of these maps in which case maybe you would like to express them as something even more efficient.
Clearly it seemed like a good idea at the time, but in the real world it just invites goofy mistakes for no real benefits.