Earlier quoted context omitted.
You can only get guaranteed protection from malware infections through the internet if you turn off your machine. Even then there might be some remote management exploits which would work on turned off machines, so unplug the cables aswell.
Thats not a reason to fudge with the definitions. The existence of sandboxes doesnt mean there are no more pdf exploits. There still are and sandboxes dont mitigate it entirely. There is also more ways then just turning off your machine. Its needlessly oversimplifying complex topics. Topics that are very interesting and have severe implications. Especially if we are talking about state level espionage. So in short, n…
The best way to reduce the number of bugs (exploits) in a system is to get rid of it.
Since you've brought up state level espionage, this might be the reason why states are run by hordes of bureocrats processing physical paperwork (this is an oversimplification of course).