I've only met two people who admitted they had schizophrenia. It seems that if it is common, most people are not super willing to announce it. The second person was probably lying, but the first made a lot of sense with the paranoid schizophrenic framing. I'd be willing to bet most that are bragging or claim loudly that they have it are looking for attention; even if they do have it. Either that or they've stretched the definition of their symptoms extremely thin intentionally for a diagnosis.
There's schizophrenia and there's the online notion of a schizo. The latter is pretty much just a paranoid sperg.
I have some peculiar tendencies which may put me in the "schizo" department. For example, I could be recommended a video by YouTube's algorithm where it says that it was uploaded "X years ago," and, upon judging the number to be ominous, I would refrain from watching it, even against my own desire. I'm not naturally superstitious, but this is one strange OCD[?] habit that I developed, I believe, from years of isolation. The more secluded you are, the more you mentally stray from the mean, from what is considered normal. But I have yet to hear whispering voices or see spectres.