if accounts does get locked because of the secret question (still not sure if it's true), then it's kind of the user's fault if their account got locked for doing something that is clearly not recommended.
also I've been wondering... it says "you are banned from using this forum!" there on OP. does that means he really got "banned" for breaking forum rules or did he got "banned" only for security? I hope a mod can answer this.
Based on the message OP got. It must've been for a security reason. I don't think those people who receives a ban has that message. Also people who gets ban here can't post outside meta, based on the latest post of OP, he can post outside. If it were a ban he could've got a ban evasion because of this so I think it's not for othwr reason other than security measure.