The journalist here is not being entirely truthful. While much of the information that the campaign used to vet JD Vance was public, not all of it was, and the internal comments are definitely not public information.

It's a bit like saying hacked internal emails are public if they are discussing public topics.

The reason the media generally doesn't publish hacked documents is so they don't create an incentive for people to hack documents. It's the same reason why many media companies won't publish pictures and sometimes names of mass shooters and child suicides.

You're free to do it. But many media companies don't do it for legitimate practical, ethical, and moral reasons.