Except I did read it and got the exact same email word for word from the same address and it was 100% legit. It is more likely that SE sent it to a sub-set of people who they believe got the wrong code without actually checking to see if they did or not. I myself followed the exact instructions and was able to finally activate my account. If i had to guess they made a new server/domain for sending the email to help with the congestion, being as the initial emails were taking 2-9 hours and this reply came withing 3-4 seconds.
As far as user names go, it is right, mine was listed as Raijitsu, which isnt my 'user name' but the handle the main SE site assigned me when i registed FF7 for the achievements. We all know SE has 323203412 million sites that all require you to relogin/register. I bet you registered that name for one of their games and just didnt remember.
Proof:
http://na.square-enix.com/us/home
When i login there it calls me raijitsu even though my forum handle is Claire, and I have a different actual user name that i type to login.