This allows you to login and change the options.
Are you sure about that? You're correct that it will allow you to log in, but it will not allow you to change the options in the WP admin screen. Using define "locks" those settings, so in order to change it, you'll need to remove it again from wp-config.php
Using update_option in wp-config.php actually changes it in the database in one step (PHPMyAdmin has nothing to do with that).
Sorry to hijack the thread and continue about this :)