That’s not what flagging something is for— it’s for posts that break the site guidelines— and that’s why the flag has been manually removed.
Headlines get changed to things that actually reflect the link's content all the time. Is flagging not a way for users to try to get that done? (I would have guessed so, but I honestly don't know. I certainly didn't flag this post.)
Flagging is commonly used to de-rank articles people disagree with, and considering the initial comments in the article, I’d eat my hat if people flagged it in good faith based on the headline alone.