I mean, I don't think that's true at all. GRRM has said the Faulkner quote many times, to him the only thing worth writing about is the human heart in conflict against itself. You have a fundamental misunderstanding of the story GRRM is telling.

Arya is in Braavos because that's where she gets to stare directly at what dissociating from her identity and personality looks like, and the true nature of death, murder and her revenge fantasies, from which she's presumably gonna turn away from, I think. Not because Martin wanted to write about the Black pearl of Braavos or whatever.