I’m making some customizations for a website, and I cam across this piece of code of a theme:

        $wpdb->insert(
            $table_name,
            array(
                'user_id'              => $user_id,
                'search_wp_query_args' => $search_args,
                'search_query_str'     => $search_url,
                'time'                 => current_time( 'mysql' ),
            ),
            array(
                '%d',
                '%s',
                '%s',
                '%s',
                '%s',
            )
        );

What’s the reason for having one more element in the $format array than in the $data array? In the docs it implies that those should have the same number of elements, for a 1-on-1 matching… Does it account for the primary key of the table, which isn’t in the $data array anyway though? Is this a bug or there is an explanation behind it?