Yes I Know The Novels Aren't Canon But That's Not What I'm Questioning Here - Tumblr Posts

In the Itachi Shinden novels Itachi mentions that his official documents were changed so that he was legally 13 when he was actually 12 (For ANBU Captain purposes) and like. How.

I understand the reasoning behind it but how would they keep that lie up? Especially with Sasuke or the people not familiar with Konoha’s underbelly. Was he just like ah yeah I know it seems like my birthday just passed but I swear it’s that time a year again. Wack. Anyway.