I would agree with you if there are people with 'latent schizophrenia' that would never have it become active but for the drug use. But perhaps it's more like someone with a heart defect that dies after some physical exercise -- there was a latent defect that would have revealed itself sooner or later (and schizophrenia is generally diagnosed by one's mid to late 20's). Does the literature have a consensus on which is the case?