Reading the link, it appears that travel abroad is currently restricted due to COVID.

Ordinarily, I don't believe Australia practices any meaningful exit controls beyond the usual: visa overstays, warrants. Certainly not capriciously based on your feelings regarding the current administration. In fact, I believe it's automated.

I remember having to do a full on interview at the airport to leave Australia. That didn’t seem normal to me

I assume they suspected you of something or your name matched a person of interest. After all, while the US has no formal interview to leave, if you're trying to do so by air, the manifest is forwarded to the FBI and DHS well in advance of departure. If they want to chit-chat, they'll be waiting for you at the gate. I've seen people yanked off the jet bridge haha.

If you're trying to do so over the land border with Canada, I believe the Canadians will notify the Americans on your way over, and happily hold onto you for a hot minute.

You'll always have to answer to an authority when attempting to leave a country.

However, ordinarily, neither AU, US nor CA will stop you from exiting. Now re-entry is another matter.

Australia is nuts when it comes to overprotecting their bio-integrity. Even withing Australia, you're not allowed to bring an apple when you're crossing a state border.

There are extremely good reasons for that:

https://www.agriculture.gov.au/pests-diseases-weeds/plant/fr...

There's a disposal bin for fruit a stone's throw away from the border. And I bet you that the apples you can buy in, say, Victoria, are imported from the same place as the ones you can buy in South Australia.

That's not just Australia. You'll encounter similar rules going to Hawaii, and even to California - although I think they have a harder time due to the number of land crossings.

Another example, specifically about apples even.

https://en.wikipedia.org/wiki/Apple_Maggot_Quarantine_Area