Erm ... mate....

A device is either air-gapped or it isn't. The clue is kinda in the name.

Yes, I know gov/mil networks use data-diodes, but that's a different kettle of very expensive fish which is certified to EAL6/7.

For everyone else, air-gapped means what it says on the tin.

Pseudo air-gapping via firewall rules is not air-gapping, its called writing ACLs.