Just because those hallucinations sometimes randomly happens to be right, people concluded that being wrong is the exception, while being right is somehow the rule.
It's like when people read [insert millenias old text here], finds a part that happens to illustrate something in their life today and conclude that it is a prophecy that predicted the future.
The meaning/truth in those is nothing more than a cognitive bias from the mind of the reader, not an inherent quality of the text.