That's a very interesting interpretation of the situation, and I'll credit it. However I can't help but feel that purposefully affecting an accent like this is inauthentic, and untrue to your real self. I can see your counter-argument that, for your brother, this act is bringing him closer to his ideal self.
I also think authenticity is a strange bird at the best of times. Humans are basically defined by their inauthenticity. In the bible, the moment humans attain knowledge is also the moment they attain the art of lying, of concealing, of feeling shame for what they are and presenting something different. It's a deep part of how we see ourselves - that we represent things, ourselves included, to persuade, to play, to organize our thoughts.
There's something funny going on with our use of the word - we call some people and cultures authentic, while others are called insincere and affected - and I don't think it's strictly related to how performative a given culture is. Somebody could be authentically Italian, and that could literally mean they perform their life at a very high tempo.
