Most AP employees sit at computers and rewrite stories night and day, it's not like a newspaper or broadcast newsroom. A few might do a little reporting or add new info to update a story. Many are stories from member news organizations, a few are AP original stories. A later rewrite was done, a new headline was written. That newsman may not have liked the terms used earlier or just wanted a new headline because of the update. The new headline may have been written by someone on their website, or an editor. We have no source so could have been from any member news organization's site but it looks like an AP site. Members can do whatever they want with the story, the byline, the headline. My point is the change most likely means nothing except someone wrote a new headline. I wouldn't guess it's because AP suddenly saw the light.

In a regular newsroom, you have reporters either coming in from an assignment and writing that story or doing phone interviews and then writing. Plus editors, copyeditors, etc. AP is a news cooperative - they have a few reporters but mostly newsmen sitting at computers and making sure all those stories coming in from members or AP reporters are ready to go out on the "wire." (No actual wire has been used since I was a very young woman.) Members give stories to AP to be shared with other members. Member newspapers, radio and TV, cable, online news then can pick and choose what stories they want to use. The reporters listed on the two bylines may or may not be AP reporters. They probably are. Cooper is either a newsman who worked the phones and added copy to the story or could be a reporter from a member news organization who added a bit to be able to give that organization a little ownership of the story. That's done often. You may also see at the bottom of a story "SoandSo Jones also contributed to this story." BTW, reporters pretty much never write their own headlines. That's true everywhere.