Does it really? Has it been found that a significant source of infections was illegal immigration? Or that without it there would not have already been internal spreading?
Doesn't matter. If you don't have covid, and nobody comes in, you won't get covid.
But that's not feasible in most countries.
Austrailia and NZ don't rely on a just-in-time cross border economy like the US and Europe. Goods arrive after being on boats which have been off shore for days or weeks.
Compare with the US-Canada "border closure", where thousands of trucks, and their drivers, have crossed each way every day all year.
That's what is happening at this moment in Thailand. There were no local transmissions for many months. Borders are closed and anyone coming into the country has to go directly to 14 day quarantine and test clean before they get out. But then some Thais went to Myanmar and snuck back into Chiang Mai in northern Thailand illegally. They were infected and have now spread the infection locally in Thailand to at least a few people. Some cases took flights to Bangkok. There is a frantic effort to track and trace everyone who might have been exposed.
But that's not feasible in most countries.
Austrailia and NZ don't rely on a just-in-time cross border economy like the US and Europe. Goods arrive after being on boats which have been off shore for days or weeks.
Compare with the US-Canada "border closure", where thousands of trucks, and their drivers, have crossed each way every day all year.