An obvious flaw is that it's comparing an entire country to a singular (and disporoprotionately wealthy) state. If you expanded the rate to America in general the violent crime rate is around 800 per 100k, and if you reduced "Australia" to "New South Wales" then you also see a similar drop - but the site doesn't provide an easy to consume summary.
The web app doesn't seem to support direct linking to query results, but it's in here: http://crimetool.bocsar.nsw.gov.au/bocsar/ under Assault - Non Domestic.
At the end of the day though - people tend to consider being murdered a significantly more disruptive event than getting punched in the face.