I wouldn't go as far as distributing the hardware wallets on different continents like they did, what if you need money urgently and a plane ticket is infeasible to get, whether it being expensive or there not being enough time?
Hardware wallets are still vulnerable to some attacks particularly to the ransom one which is possible in the case the computer you have to connect to is compromised.
I don't understand what you're talking about here, because hardware wallets are designed (at least some) to be safe to use even on an infected computer - because every action must be confirmed at the touch of a button before execution - which means everyone has complete control in their hands. Two dangers lurking on wallet hardware users are clipboard malware and fake sites that mimic original sites and require users to enter their seed.
Doesn't mean you should do it though, it's never worth the risk.
Airgapped machines are just one part of the measures - you either want to keep a low profile, so robbers don't find you, or else, store the airgapped machines and hardware wallet in a high-security room with alarms, cameras, Kensington locks and such, useful when you are trying to protect dozens of bitcoins.