[According to the Codex](https://wordpress.org/support/article/roles-and-capabilities/#special-cases), all that's needed to enable the `unfiltered_ upload` capability - i.e. the ability to upload *any* filetypes to the Media Library rather than just the default whitelisted ones - is to set:

    define( 'ALLOW_UNFILTERED_UPLOADS', true );

...in wp-config, which I have done and placed above the line where it says to stop editing. 

Most online articles about enabling the capability suggest it's sufficient to stop here, including [an answer](https://wordpress.stackexchange.com/a/161875/167562) on this very site, but the Codex itself suggests that it's necessary to actively assign the capability to users, which I've also done, in my theme's `functions.php` file:

    $edit_admin = get_role('administrator');
    $edit_admin->add_cap('unfiltered_upload');  

However, despite this, whenever going to my Media Library to upload a non-supported file (so far tested with an .AI file and .SVG file), I still get the standard error:

> Sorry, this file type is not permitted for security reasons.

Why is this?