First thing, I am not Korean. Second thing, there are cultural differences that you are unaware of. People around the world do not behave and think all the same. Its not a matter of race or whatever thing you're trying to associate it with.
People just don't do such things here. Is it because they are well behaved? No, but its just not in the mentality here. They don't find it funny to edit pictures and spread fake news. They find funny to do other things that trust me you and I wouldn't find funny as well.
There can be exceptions to the rule but what I can say is that when people post pics on a Korean forum, they probably dont even think about the possibility of making a fake. It does not even cross their minds. And the test cars being all around these days, there are so many pictures of the Stinger F/L at the moment (less than 10% reach facebook or this forum).