It's something akin to a service provider in SAML parlance, if we are to believe reporting. How can it be air-gapped?

And if we are to believe the hacked company, it is a development environment with test data in it. That remains to be seen, but is a risky thing to lie about. If there is production data in the leak, we will surely know about it.

At the high end you can use data diodes to isolate critical data.