Umm, nope. I don’t think the author ever claims that the inmate believes in Sufism. Far from it-it deals mainly with the widespread prevalence of mysticism and superstitions throughout Islam and points out that Sufism is unlikely to be of any use.
So, why bring up Sufism? Why does he open with a reference to it? We are supposed to think the inmate and his freaky fantasies are somehow related to it? They’re not.