I think it's less a character being correct about everything as it is that most characters tend to come across situations where their knowledge on random topics is tested unless they're an adventurer or some kind of student. A PC alchemist who never stepped foot out of Gridania would obviously know a lot about potions, but if questioned on the current happenings in Ul'dah, they wouldn't have the foggiest. Meanwhile in real life, people have access to so much knowledge through books and the internet that they can have all kinds of odd interests.
As for Koen, he knows what he's experienced and, while not the smartest guy, can figure out basic details of related events. He was there when the Monks were wiped out, and he knows they were labeled as heretics, but he realises they probably pissed off the King of Ruin at some point and that the attack was more political than anything. On the other hand, if he somehow came across some kind of Sharlayan ruin, he wouldn't be able to tell you anything about it, and would just shrug if someone asked his thoughts.
Obviously there are more things than not in the lore that he's completely unaware of, but as for ideas of his that are entirely wrong, it's nothing too major. To give a few examples: he thinks Elezen's pointed ears are just decoration to make them look less like stretched out Hyur; he thinks volcanos are mountains that grew too high and got melted by the sun, and he's positive that most Gridanians walk around in their underwear.
The majority of this misinformation is just because he doesn't have anything other than hearsay and guessing to go off of. He's never been to Gridania, so when someone tells him they walk around mostly naked to be closer to nature, he figures that makes sense and believes them and probably will do so until someone argues otherwise, if it ever gets brought up in a conversation.
As for Koen, he knows what he's experienced and, while not the smartest guy, can figure out basic details of related events. He was there when the Monks were wiped out, and he knows they were labeled as heretics, but he realises they probably pissed off the King of Ruin at some point and that the attack was more political than anything. On the other hand, if he somehow came across some kind of Sharlayan ruin, he wouldn't be able to tell you anything about it, and would just shrug if someone asked his thoughts.
Obviously there are more things than not in the lore that he's completely unaware of, but as for ideas of his that are entirely wrong, it's nothing too major. To give a few examples: he thinks Elezen's pointed ears are just decoration to make them look less like stretched out Hyur; he thinks volcanos are mountains that grew too high and got melted by the sun, and he's positive that most Gridanians walk around in their underwear.
The majority of this misinformation is just because he doesn't have anything other than hearsay and guessing to go off of. He's never been to Gridania, so when someone tells him they walk around mostly naked to be closer to nature, he figures that makes sense and believes them and probably will do so until someone argues otherwise, if it ever gets brought up in a conversation.