Yeah, the wikipedia article addresses this somewhat;
The name of the mountain was previously spelt "Mount Kosciusko", an Anglicisation, but the spelling "Mount Kosciuszko" was officially adopted in 1997 by the Geographical Names Board of New South Wales. The traditional English pronunciation of Kosciuszko is /kɒziːˈʌskoʊ/, but the pronunciation /kɒˈʃʊʃkoʊ/ is now sometimes used, which is substantially closer to the Polish pronunciation [kɔɕˈt͡ɕuʂkɔ]
You're not wrong unfortunately. It hurts me on a few levels when I hear the pronunciation butchered by pretty much all Australians. I understand why / don't hold it against them, but it's still totally wrong pronounciation.
It's hard to do it correctly if your native tongue is not slavic. I'd like to be wrong though.
They should know the name, though. Yup.
If anyone's inclined towards random wiki trip I suggest reading about Strzelecki, who named the moutain. He was an explorer.