Youtube is the hook for copyright infringement of its millions of members, who each have the ability to upload at will ... they use computer driven checks to validate what you are posting and warn you if titles or descriptions alert them to possible copyright violations. Greensleeves probably has hundreds of copyrights registered (probably all for arrangements) so Youtube check flags go off, and they tell YOU to sort out the flag issues, if you disagree.

And by the way, that process the set up to solve the issue does work. They flagged one of my videos (for Poor Wayfaring Stranger). I contested the status through their process and it worked.