most likely they were already passed a certain point when you disabled it, allowing them to complete registration.
I usually delete them as they come in when I am online. I was a spark camp all day yesterday and this morning, so those 64 that you deleted all registered after I left yesterday morning, so we got 64 bots within 24 hours.
It is getting old, and as of now we can't really stop it. They are all different IP's so it's not like we can just ban a few and that's that.
It could have something to do with the updated server or something? We didn't have this problem up until the update.
(grant it, the CAPTCHA was not working, so perhaps people and bots couldn't get through. lol)