It may have happened automatically at submission time. Otherwise, my best guess is that it appeared like an editorialized title.

https://news.ycombinator.com/newsguidelines.html

how is it editorialized? it matches the title of the article. removing part of that title is editorializing.

I have noticed that about an hour ago, so I don't think it was automatic. I guess I'm just curious why it was found to be against the guidelines or not representative of the topic in the post.