The High Court does interpret constitutional legislation

That's not whar was argued though. Stop lying. Actual quotes from the article:

• The High Court would ultimately determine its powers, not the Parliament.

Incorrect. The referendum amendment clearly says parliament will have the power to make laws with “respect to matters relating to the Aboriginal and Torres Strait Islander Voice, including its composition, functions, powers and procedures”. Legal experts – including Australia’s former chief justice – say high court challenges are unlikely and even then, the court cannot change a decision made by parliament. It can only send a matter back for reappraisal.

And later:

• Once the High Court makes an interpretation, Parliament can’t overrule it. We will be stuck with the negative consequences forever.

Incorrect. Legal experts – including the former chief justice of Australia – say the high court cannot change a decision made by parliament. It can only send a matter back for reappraisal.

Nowhere did The Guardian claim that the High Court doesn't interpret constitutional legislation. That's a complete strawman invented by you.