File advanced not rendered correctly

Hi, I've tried to add a File advanced field in a custom post type using the same example provided in documentation:

 $meta_boxes[] = array(
            'title'      => 'File',
            'post_types' => $this->post_type_name,
    
            'fields' => array(
                'id'               => 'file',
                'name'             => 'File Advanced',
                'type'             => 'file_advanced',
            
                // Delete file from Media Library when remove it from post meta?
                // Note: it might affect other posts if you use same file for multiple posts
                'force_delete'     => false,
            
                // Maximum file uploads.
                'max_file_uploads' => 2,
            
                // File types.
                // 'mime_type'        => 'application,audio,video',
            
                // Do not show how many files uploaded/remaining.
                'max_status'       => 'false',
                'multiple' => false
            ),
        );

but the control is rendered as 7 plain input controls.

I'm using WordPress 5.7. It makes no difference if I set Gutemberg or classic editor in the post type settings.

Kind regards, Luca