Config files should not be merged

[chosten]

I can't remove the 'auth' file because it is in the default configuration.

Or if you plan to add more config options later, then you should move the files in a sub key. That way you can keep the merge.
Something like:

return [
    'files' => [
        'auth',
    ],
];

[bernhardh]

Yeah, that would be a great feature!