(I am not a psychologist!)

Visual hallucinations are not a hard criterion for diagnosing schizophrenia. They do occur, but the symptoms are more about delusions, disorganised thinking and catatonic symptoms. IIRC hallucinations are more often auditory, like hearing voices.

Think of it as a continuous spectrum from the idealized normal person (the center of a bell curve) to the person having significant problems living a normal, fulfilling life. The eccentric personality is somewhere in between.

This is all about definitions. The ICD-10 and similar categorizations essentially work by listing a number of symptons and a minimum count of symptoms a patient has to have to be diagnosed according to this definition. They don't make any assumptions about disorders existing per se.

I think it's far more acceptable for us to "mishear" something and think nothing of it. The seeing also have the backup sense, sight to verify much of what we hear.

"I heard the sound of an elephant stomping around in my living room."

This statement made by a seeing person could be made by nobody thinking much of it. I wouldn't immediately ask if they actually thought an elephant were in the living room at the time.

The same statement made by a (blind) schizophrenic person could have implied that the person actually believed there was an elephant in the living room, but the clinician might have missed the significance and not asked follow up questions.

A bit of a contrived example, but you get the gist.

To a seeing person it might

It’s not like screening people for spectrum or personality disorders.

Note, my sample size is far too small to draw universal conclusions about schizophrenic.

Since blind people need to rely on others a lot more than people with sight, I think it would be even harder for them to avoid medical authorities than for other schizophrenics. For what it's worth, the schizophrenics I knew personally were not averse to seeking help for their condition, but were very distressed by side effects from medication (understandably!)

There's a strong cultural component to how schizophrenia manifests. Violent, paranoid thoughts are more common in societies like the United States. The extent to which their experiences can fit into a positive cultural narrative partly dictates their quality of life. The U.S. is exceedingly hostile in that regard. You're likely better off in a society where hearing voices is considered a gift from the gods, or where perceiving odd but intriguing cause+effect relationships suggests you can sense magic.

Googling will show similar reporting in the literature over several decades. I don't think I've seen any contradictory research, though that's not surprising as this is just an interesting observation; there aren't any sophisticated, concrete explanatory models to critique--individualist vs collectivist dichotomy seems intuitive but not concrete on its own. Rather the focus seems to be on pragmatic therapy. It's noteworthy nonetheless, particularly as a reflection of American society, and of how culture informs pathology, a point usually made regarding more touchy-feely mental health issues and thus lacking punch.