Be patient with Australians. They have have a terrible tradition of vicious racism.
The indigenous people of Australia were only considered part of Australian society (e.g. counted in the census) in 1967. As a New Zealander visiting Australia the casual racism of white Australians is mind blowing. New Zealand is not free from racism, far from it. Australia is next level
It will take a few generations for Australians to come to terms with living on stolen land, and to adjust to being colonisers. (White New Zelanders, Pākehā have been doing this for over thirty years, it is a process)
It is odd to put that declaration on a web page, how a digital asset is comparable to standing on land is clearly something the Australians are working on. Good luck to them, move on and let it be.
Let he who is without sin cast the first stone
What exactly is supposed to happen though? "Don't be horribly racist" is a nice idea, but it's not like we see people who put these acknowledgements up actually attempting to return the "stolen land"
I think it makes sense to put it on the website if you're going to do it though, since it's a website about, basically, a building in melbourne.
Acknowledgements of Country are not uncommon on Australian web sites, especially with arts organisations. Sometimes they're in the footer, sometimes as an interstitial. They're also common in speeches/formalities.
Edit: I'd agree though that NZ has a more mature perspective, stronger Maori population and that the condescension is probably fair.