It often does colloquially refer to schizophrenia, I've heard people use the word this way for as long as I can remember. General purpose English dictionaries document this colloquial meaning, I checked several to be sure:

"(archaic) schizophrenic" https://en.wiktionary.org/wiki/schizoid

"characterized by, resulting from, tending toward, or suggestive of schizophrenia" https://www.merriam-webster.com/dictionary/schizoid

"suffering from or behaving as if suffering from schizophrenia" https://dictionary.cambridge.org/dictionary/english/schizoid

"Informal. of or relating to schizophrenia or to multiple personality." https://www.dictionary.com/browse/schizoid

"Someone who is schizoid has schizophrenia" https://www.collinsdictionary.com/dictionary/english/schizoi...