This is explained if you click through the link to the Samsung post about this issue.
> Australian mobile operators and Samsung have identified a number of older mobile devices that will not correctly connect to an alternative mobile network to make Triple Zero calls when the customer’s primary mobile network is unavailable. These devices need to be updated or replaced to make sure they work reliably in an emergency.
> Australian mobile operators and Samsung have identified a number of older mobile devices that will not correctly connect to an alternative mobile network to make Triple Zero calls when the customer’s primary mobile network is unavailable. These devices need to be updated or replaced to make sure they work reliably in an emergency.