Why is the end of Taylor Swift and Matty Healy's situation being reported as a breakup if they weren't dating exclusively?

TMZ reported yesterday that Taylor Swift and Matty Healy are no longer doing whatever they were doing when they were doing it. Other outlets are now following that lead, including PEOPLE with their “exclusive” story about why Taylor and Matty “broke up”:"She had fun with him, but it was always casua...