Okay, I figured it out maybe. These accounts could be compromised, for I was just contacted by one of them dormant accounts offering up a service.
Please look into this. Or let me know if I'm a crazy fuck.
Bruno
It shows up if a user has logged in with their last login time being at least 6 months ago.
I believe a password reset can be done before a login event, which is why the times are like this in the log.
I'd speculate a lot of the accounts waking up are indeed compromised but not all.
For reference:
https://bitcointalk.org/index.php?topic=1913950.0