It's a cartoon caricature of Australia dreamt up by American franchise operators, ergo "worst Australian food" .. not even remotely like Australian food.
Logically and linguistically it isn't equivilant at all.
Let's say hypothetically that the US has the best Mexican food - even better than Mexico itself, and that food is sold in Food Truk X that tours about in Dallas Texas.
Taco Bell still exists and (it seems that) you are open to the notion that Taco Bell is terrible terrible "Mexican Food".
Ergo, the US has both the best and the worst Mexican Food.
Outback Steakhouse is the worst "Australian Food".