The safe choice is to declare the incident and let the Australians figure out whether they care or not.

Answering yes to that question does not result in an automatic refusal -- no country's goverment would be so stupid as to give every other country in the world a heckler's veto on who they are going to let in. (E.g., if you were once refused entry at the Brutopian border because you had written a letter to the editor criticizing the human rights situation there, I doubt the Austrailans would count that against you -- except if you try to hide that fact from them when they ask you explicitly).

Australia wants to know about previous immigration trouble because it might point to something they care about. But they want to decide for themselves what they care about, not to have applicants try to make that determination for themselves.

The safe choice is to declare the incident and let the Australians figure out whether they care or not.

Answering yes to that question does not result in an automatic refusal -- no country's goverment would be so stupid as to give every other country in the world a veto on who they are going to let in. (E.g., if you were once refused entry at the Brutopian border because you had written a letter to the editor criticizing the human rights situation there, I doubt the Austrailans would count that against you -- except if you try to hide that fact from them when they ask you explicitly).

Australia wants to know about previous immigration trouble because it might point to something they care about. But they want to decide for themselves what they care about, not to have applicants try to make that determination for themselves.