The conditions in the agreement between arm and Apple aren't public so you can't say for sure. Historically arm hasn't allowed architecture licensees to do their own thing. You're implementing arm standard architecture (and passing the conformance test suite) or nothing. Looks like they've given Apple some special dispensation to do things differently (e.g. the custom AMX instructions that have been uncovered https://gist.github.com/dougallj/7a75a3be1ec69ca550e7c36dc75...).

For ARMv9 this potentially means they can pick and choose what they want to implement. I'm sure Apple has had plenty of input into the specification (along with other partners).