When the narrator's brother claims that the narrator "went on to wait for an official appointment," it is a metaphor for the idea that the narrator has gone on to be convinced by officials (a.k.a. leaders who believe in the traditional ways) that the old ways of their society are the right way to live. While some may believe that the brother is telling a lye, which would still perpetuate the idea of "cannibalism," I believe the brother is telling, in a metaphorical sense, the truth. The narrator has been taken in to be healed of his "delirium" by those who impose the ways of tradition on society ("officials").
While it may not be obvious, there is a difference between being cured and being "eaten". If the narrator was eaten, this would mean that he was one living in the traditional ways of society (the "cannibalistic" society he dwells on and would be "devoured" by others in the society, for the idea is that the traditions of this culture cause people to metaphorically eat away at each other. Being cured means that the narrator does not believe in these traditions and is being taught to believe it is the right way to do things. To become apart of these traditions is to be "eaten", so either way the narrator would be "eaten."