this value comes from the template tag the_author()
.
You can also filter this.
But it is important, that you check, that the filter only work on the feeds; see the follow example at the check for is_feed()
.
After this i change the autor name only, if the string has the value ‘name_xyz’; here is the point that you change your data from your requirements.
I write from scratch, don’t tested!
add_filter( 'the_author', 'fb_change_fead_creator', 10 );
function fb_change_fead_creator( $text ) {
if ( ! is_feed() )
return;
if ( 'name_xyz' == $text )
$text="my new name";
return $text;
}
Best