Ok this is confusing me now. That stats page stopped updating the history at the bottom of the page in December so I thought it had completely stopped updating. I know when users are banned or nuked their accounts remain and even when people have asked to have accounts deleted they are told they can't. So I cannot explain it other than to take a guess that they used to delete accounts a long time ago and stopped.
Theymos is more lenient with the rules with advanced members who have ranked up quite a bit and have aged accounts.
Quite a few users of legendary status have had their names changed by the admin (though I'm not entirely sure I'm allowed to state all of them, I don't think theymos would mind me mentioning hilariousandco's namechange).
In the forum's first couple of years, accounts would sometimes be deleted. Also, in rare cases an ID can be skipped (eg. if a database transaction gets rolled back).
This makes more sense and was what I was thinking - just seemed a little odd (shows you coded the stats page well theymos!)
This sort of raises up more questions than it answers, especailly who had the uid2 (though this is taking this discussion a bit off topic so I will refrain from posting anything on that here).