Air gapping is not a total barrier.

(you still need to get data in and out sometimes, Chips can be misused as radio antennas, loudspeakers can be used as microphone and do ultra sonic data transmission to other devices etc, so still making sure the software is under control on the Air gapped computer sounds like a good idea)

That's the point, you'd think any browsers should be fine? But only Firefox was approved after OpSec department did their research. There were definitely something that made them very unhappy about Chromium to ban it wholesale.

You can import/export a lot of data with just sound and video.