There is an alias mapping which is updated by admins periodically:
https://github.com/moodlehq/moodle-local_dev/blob/master/db/install.xml#L70
https://github.com/moodlehq/moodle-local_dev/blob/master/admin/git-aliases.php
Actually it would be a cool feature to make that a self service thing to claim your alias for 'current' email addresses - send an email with a token to the email address and let the user link them. It's actually a bit of a pain finding peoples real moodle.org accounts through the millions of accounts.