Former State here. In a hurry so I only browsed a few of the declassified cables. My first blush take is that the "AI" is sorting and examining cables classified at or below the "Confidential" level limiting the danger of exposure - most "confidential" documents present very limited exposure danger.

Additionally, by State regs, all cables older than 25 years are already considered declassified automatically, and the examples presented (the random ones I saw) all fall under that category. By extension, I'm assuming that the AI is only targeting this lower classification, scanning and applying certain rules, with a resultant output that may be reviewed by a human with much less rigor making their job a bit easier.

I'm quite confident that under no circumstances is any cable at the "Secret" level, even if 25 years old, released without very rigorous examination. This would require NSA agreement, which in context, would be quite the hill to climb.

So to a degree, the press release is a bit self-serving ("we're keeping up with the times") and I'm not entirely sure that the process is much beyond keyword searching of lower classified cables that themselves already presented very limited exposure danger.