The difference is: the first duplication was for one of the function's direct arguments, and this is for an argument of an argument.

Currently this shows up as:
`Type: Function( Object elementOfArray, indexOrKey ) => Object`

Ideally it would show up as:
`Type: Function( Object elementOfArray, Integer or String indexOrKey ) => Object`

You can duplicate the entire `<signature>` of `map()` - one with `indexOrKey` being type String, another with it being type Integer - but that would be extremely confusing to the user. It would also produce two identical hash URLs.