While they make a number of good points, I'm not sure I agree that air gapping is as unhelpful as they say.

The hard point BitBox points out is that you are always relying on a potentially compromised device to assist with psbt creation, or transaction broadcasting, or even just knowing what coins you have.

The risk is not so much in storing your keys as it is in using them to sign. This is one reason why the language of "hardware signers" is better than the language of "hardware wallets".