"The crucial detail of how the X-rays create the pressure is the main remaining disputed point in the unclassified press."
Then the article goes on to list the three leading theories. This seems like something you can probably evaluate for sure with a few bomb tests, again, if allowed by the controller of the planet, the USA.
I've played with smaller unrestricted local models and they will tell you how to make a bomb with easily available items as well as where to source them. I don't doubt that these >1000B frontier models have better information.
If the information is in the corpus then it's also in the public Internet and/or in books. The safeguards are there not because the model knows non-public information, but because it's a bad look for the model to dispense that information.
>they will tell you how to make a bomb with easily available items
Making a chemical explosive is trivial compared to making a nuclear weapon.