Explanation for Thursday War thread lock?

Can a moderator please explain how The Thursday War preview is considered leaked information? I just don’t understand. It seems to me that since it is a preview on an official site then it would be the same as a trailer or gameplay footage.

As of right now, that content is being considered leak content. I assume because it wasn’t meant to be shown yet, but it was. Why it was released as it was, I’m not sure why.