I didn’t think banks were allowed to make such offers any more?
They aren't. Entire retention team probably got made redundant when this was legislated. If you look at National Consumer Credit Protection Act 2009 (Cth), Chapter 3 - Part 3-2B, Division 8, 133BV
Credit provider not to suggest the consumer not terminate the credit card contract
When this section applies
(1) This section applies if:
(a) a consumer who is the debtor under a credit card contract has a credit card termination entitlement under the contract; and
(b) the consumer has requested to terminate the credit card contract.
Requirement
(2) The licensee who is the credit provider under the credit card contract must not suggest that the consumer remain in the credit card contract.
Civil penalty: 5,000 penalty units.
Offence
(3) A person commits an offence if:
(a) the person is subject to a requirement under subsection (2); and
(b) the person engages in conduct; and
(c) the conduct contravenes the requirement.
Criminal penalty: 50 penalty units.