Of course they could if they really wanted to, but as as been admitted many times by the state governments, there is not automatic screening of any passengers.
You could write on your form you were transiting from Timbuktu (joke) and no one would blink. So if you tick NO to international arrivals, unless you are wearing a lei around your neck, a Hawaiian shirt, sipping out of a coconut and with international bag tags dripping off you there is no way they can tell on the spot
They’d have to pull you aside, do a full screen and search and clearly this isn’t happening…
Of course I’m not advocating people do one thing or the other, that is their choice - just pointing out that the screening is just a scary show.
So someone could fly into Sydney then jump on a plane to Adelaide and tick NO and that would be that, unless there was some reason to pull the passenger off and do a full interrogation…