Admin to activate user account not working properly

I think it was 2 days ago that I set the account activation to admin only, but I've had 2 users that got the mail to activate their own account.
The two are just the ones I know of. So, what's going on?

I set it to admin only cause I had spammers that kept making accounts and saying rude things on the forum, yeah I banned them all and everything but, what's the use of admin only account activation if some members get through like that.

I asked my moderators if they got any letters, they said no. And I asked one of the members that activated it by themselves and they said they got the letter. Me and the other admin didn't get anything.

Try doing the option again? Clicking user and saving and then clicking admin and saving?

I tried that. I just had a girl signing up by themselves now.