I think the emphasis is being placed in the wrong area. Diagnosis come and go. The real issue are his symptoms well managed. If they are his diagnosis is irrelevant. If they are not his medication needs adjustment so he can live the most fulfilling life possible and that is where i would place my emphasis.
The problems you describe are called negative symptoms and are part of his schizophrenia. So his medicine is helping with the positive problems like delusions and hallucinations, but not the negative ones. Although the hardest they need addressing as well.
Hello,Please feel free to ask questions that is what we are here for. The best answer is a combination of the right medication and psychotherapy, but negative symptoms are the most difficult to correct.