"Air gapping" just means not connected to the internet, directly or indirectly.

Usually goes along with the air gapped system running in a small intranet you strictly control access to.

Its not a bleeding edge technology as the article says (maybe the author made a joke?) but a standard security measure to protect highly sensitive or critical systems.

It is simply isolated data center racks for government. Just like AWS gov cloud. Apparently the article author had never heard the term "air gap."

I don't have first-hand knowledge of this tech (if i did i probably wouldn't be able to comment) as i haven't heard anything about this during my time there, but if I had to guess, it's probably a silo'ed GCP environment on silo'ed Borg cell on silo'ed turtles all the way down to physical hardware and facilities.

It's explained in the linked article.