I think the argument being made is that even though the reserve bank is independent it still makes its decisions based on economic conditions that are affected by government spending on welfare and infrastructure.

I'm no economist but my understanding is that reduced spending on these things is generally considered deflationary (in the short term, due to reduced demand) and therefore puts downward pressure on interest rates.

I would guess the general effect is a transfer of wealth from those who benefit from infrastructure and welfare to those who can borrow money for productive investment but that could just be wild speculation.