That, quite frankly, is a load of absolute codswallop.
Far more asylum seekers arrive by plane than by boat, and by far boat arrivals are more likely to be found to be genuine refugees, and that's not because of some absurd notion that somehow Immigration goes soft on boat arrivals, tell that to the genuine refugees banged up on Christmas Island and who still haven't been released to the community because ASIO hasn't got around to giving them security clearances.
It will be as long as falsehoods like the one above persist, and people in the media and in parliament continue to exploit the issue by using it as a dog-whistle to appeal to the baser elements in Australian society.