Lots of food types that are not geographic indications have strict requirements on ingredients, process, finished product.
The geographic restriction for "feta" serves no purpose except to favor the producers who lobbied for the geographic indication. You could strip off the geographic restriction, and you'd have a normal food quality regulation.
> I also note that most "feta" cheese made outside Greece is actually made with cow's milk.
Feta cheese has been made throughout the Eastern Mediterranean for ages, primarily using sheep's and goat's milk. There's nothing particularly special or distinctive or uniform about Greek feta. The historical reason why the geographic indication is limited to Greece is that it was created by the Greek government (i.e., it was a protectionist measure passed by the government to benefit its own cheese-makers). Greece then lobbied the EU to adopt the geographic indication. That's why the PDO is limited to Greece - not because what the Greeks call "feta" is different from cheeses produced in the same way right across the border in Macedonia, Albania, Bulgaria or Turkey.
So you insist, but it's clear to me you do this without any substantial knowledge of feta, or the similar cheeses made around the area, other than what a quick googe could tell you.
In truth, it takes rather more than a quick google to realise that what you say is wrong. The other cheeses that are similar to feta and made in the Balkans, Turkey, Romania, etc, are almost always made primarily with cow's milk, sometimes with added goat's milk. Why? Because cow's milk is cheaper. Why? Because cows produce a lot more milk than sheep. Individual cows produce double or triple the amount of milk of individual sheep and cows can be milked all year round whereas sheep are only milked between February and September.
Even in Greece, non-PDO cheeses made in the style of feta (or other PDO cheeses like kasseri) are made with cow's milk, again because it's cheaper because it's more plentiful. More precisely, those non-PDO cow's milk cheeses made in Greece with cow's milk are made with cow's milk imported from nearby countries that have substantially larger dairy cow herds than Greece.
Greeks make most of their cheeses with sheep and goat's milk (pretty much every single Greek PDO cheese is a sheep and goat's milk cheese, except for Metsovone, St. Michali, Kopanisti and Graviera Naxou and the latter two can also be made with sheep and goat's milk). This is actually a very stringent restriction and it gives an easy advantage on price and profitabilty to cheeses made with cow's milk, which is why the most common adulteration of Greek PDO cheeses is with cow's milk imported from Bulgaria, Turkey, etc.
So basically what you say is completely wrong. Greeks are forced to make their cheeses according to the PDO regulations. Everyone else is free to make theirs any old way they want. That's why Greek feta is different than other cheeses in the region. It's the market forces.
You keep making assumptions based on incomplete knowledge of the cheese market and then you state these assumptions with great certainty, even though they are completely wrong. Please don't do that, that's just spreading misinformation.
This is not true and you don't know things as well as you think you do. PDO regulations absolutely focus precisely on ingredients, process and the final product.
For example, PDO regulations for feta stipulate, among other details, that it must be made with sheep's milk with the addition of up to 30% goat's milk and that the milk must come from animals born and bred in the Greek regions of Thessaly, Thrace, Epirus, Macedonia, Central Greece, Peloponse and Lesvos, from the breeds adapted to the area and reared by traditional methods. The fat content of the milk must be at least 6% w/w and the pH of the milk before the cheese is made must be at least 6.5. The milk must be made into cheese at most 48 hours after milking. The finished cheese must be aged for at least two months in brine containing 7% NaCl w/w. The final product must be a cheese "distinguished by its slightly acid and salty taste and its properties of mild lipolysis" (lipolysis imparts a piquant taste to cheese), with a maximum water content of 58%, minimum fat content of 43%, and 2% salt in water. There are more detailed instructions here:
https://ec.europa.eu/geographical-indications-register/eambr...
So the PDO regulates the provenance of the sheep milk, as well as the location the cheese is manufactured, but obviously the focus is on the quality and organoleptic characterisics of the ingredients in the specified territories, and that because the same characteristics are not reproducible in different territories (for example because the breeds of milk producing animals are different and the flora they feed on, and therefore the soil bacteria that flavour this flora, are different).
I also note that most "feta" cheese made outside Greece is actually made with cow's milk. For example, this was the case with French, German and Danish "feta" before Greece successfully defended its PDO and it is still the case today for feta made in the US. I'm not sure about Australia, but it's probably the same there. In Greece, cheese made in the same way as feta but with cow's milk is called "telemes" and is also a PDO cheese.
As far as I can tell, no "feta" cheese made outside Greece has the piquant taste imparted to cheese milk by lipases, that characterises Greek feta.