An application asks the OS for the list of printers. The question is what should an OS with no support for printing do. The article says it should return an empty list. My point is that it should pop up a notification directly to the user telling them "hey, the app you're using is trying to access printing, but that's not supported on this machine" or some other language like this (it could then return an empty list).
Trying to enumerate printers doesn't imply that the application will use them, it could easily be part of the initialization of some framework, shared library, language runtime, or whatever. Unless there is some actual user interaction, there is no way for the OS to know what the user is trying to do. It is best to err on the side of not making assumptions.
