I mean, someone who researches security of airgap computers continually coming up with new ways to break them, seems like the expected outcome. Its their job after all.
I would start by asking what they need computers for.
You don't really need one to read text from a screen. Of that most would be old documents that for the most part should be public. What remains besides reading is most likely 95% stuff they shouldn't be doing.
The most secure part is the stuff we wish they were doing.
I’m having a real hard time understanding what this comment is saying. Are you asking what high side computers are used for besides reading classified information?
Maybe, I could also be asking why you would use a computer if all you want is to read documents.
If you have an operator send a telegram for you that person is capable of doing a lot more with your text than you want. On the other end is another telegram operator to further increase the risk. You might want to send a letter in stead. It's slower but more secure.
If you want to read text from a monitor a computer is super convenient but like the operator it can do other things you don't want. You don't need a computer to put text on a screen. Alternatives might be slow and expensive but in this case you don't have to send things to the other side of the world. That would be the thing you specifically don't want.
