Yes, a completely airgapped system is likely much more secure. It's also much less useful. Conditional on the model's having enough contact with the outside world, a sufficiently capable model is able to basically do whatever it wants.
If I test out my backyard cannon and blast a 10 foot hole in my neighbor's wall, “a cannon that can't smash through walls isn't useful” probably won't be a great defense in court.
If I test out my backyard cannon and blast a 10 foot hole in my neighbor's wall, “a cannon that can't smash through walls isn't useful” probably won't be a great defense in court.