As far as I can remember Alpha never really tell Akira anything about the other project nor is about the non-interference rule. Alpha really never tell him that Katsuya is also old world user nor she tell him about the "any" other old world user.
however she did explain why everyone think Akira...
that's her point in training. outside of the palace she's basically her own. she need to be able to navigate them to survive in that world as madam of house.
police? she's pretty much above the law and so does everyone in that place.
its the culture of the empire. don't mix it with RL culture.
to be honest, I don't understand the point of the conversation.
so she pretty much just want to share story? it kind of too deliberate to create moment just to share story.