To me it just seems like a way to harass and disrupt journalists trying to closely cover the story.
Messing with the press will always be construed as intimidation. Means to an end. And rightfully so. So as the government; just don't do it. Don't even think about it. The press doing their job is the turning point in the feedback loop that makes democracy work.
The first amendment protects the press, as well as the people's right "...to petition the government for a redress of grievances."
The whole "keep tabs on journalists to learn more about the violence that journalists didn't contribute too" is a strawman argument, and a fairly obvious boot-licking one at that.
Suddenly? No. This is the inevitable result of the normalization of authoritarianism, militarism and mass surveillance that began after 9/11.
I mean, we have a President who outright calls the press enemies of the people, and half the country agrees with him, and most of the rest just dismiss it as Trump being an angry crazy man. That's how far the Overton window has been pushed towards protofascism in the US.
"CBP told our colleagues at NBC News that the names in the database are all people who were present during violence that broke out at the border in November. The agency also said journalists are being tracked so that the agency can learn more about what started that violence."