Don't get me wrong, they absolutely can DMCA you if the hosting is in a foreign country iirc.

I was under the impression thr prescedant was:

Data Access Corporation v Powerflex Services Pty Ltd (1999), alongside specific provisions in the Copyright Act 1968.

The australian DMCA is called the TPM, it's more aimed at Bypassing, decrypt, or circumvent a digital lock or DRM (Digital Rights Management) protecting copyrighted material.

I do not think that phantom notes are encryption or rights management.

If you do your hosting in australia for your code/software, the US companies will probably have a bad time trying to convince the australian courts that access is the same as copyright infringement.

I'm not a lawyer, but i'll be damned if the 'vibe of it' shouldn't be a legal defense.