It sounds like they are over-complying in response to recent legislation:

This is due to an update to the ‘Emergency Call Service Determination’ (ECSD), in the explanatory statement it says:

“Subsection 6(2) directs ACMA to include requirements for providers to identify mobile phones unable to access Triple Zero, notify the user, provide assistance if necessary to access an alternative mobile phone, and cease providing service to the affected device. Providers will also be required to not provide service to a prospective customer seeking service with an affected mobile phone. This requirement makes clear the responsibility providers have to ensure mobile networks provide access to the emergency call service.” […] “The amendments to the Determination to be made under section 6(2) are to be determined and commence in full by 1 November 2024.”