Harry is totally schizophrenic in MOR though. He's got all of the Founders in his head.

You seem to be working from a unified view of the mind in which there is one single personality with one single voice, and deviations from this structure are pathological. I don't think this is accurate.

Even if it was, it is common for people to hold internal dialogues, and not unusual for patterns to develop where certain kinds of thought are given certain labels. I don't think this says anything special about Harry, except that he has a rich and vibrant inner life.

Also, a Public Service Announcement: "schizophrenia" is an umbrella term for a long list of possible symptoms whose main common feature is disconnection from reality or warped perception of it. You are thinking of Dissociative Identity Disorder (commonly known as Multiple Personality Disorder), which is a completely different thing altogether.