Seems unlikely. First, confirmation bias has its limits and normally is never capable beating direct observational evidence. Second, people basing their identity on their being Jesus sounds like a plausible idea, but identity based on the fact that my arm isn't paralysed not that much. Third, it takes some time to associate own identity and status feeling with an idea - one doesn't become political partisan overnight - while the anosognosic delusions emerge immediately after the brain is damaged (well, I suppose this is so, but I can easily be mistaken here).