The code to fetch the elements from a Craft Element Query is different when the elements have been eager-loaded. For example, to get the first element of a non eagerly loaded field, someField.one(), but for an eagerly loaded field, someField[0] (and that doesn't even get into the error checking). With Agnostic Fetch, you can do someField | one (or one(someField) or craft.agnosticfetch.one(someField)).

The Agnostic Fetch functions are available as twig filters, as twig functions, and as craft variables.