A schooner is actually three quarters of a pint
Australians have traditionally used different glass sizes in different states and have had the same names for different glass sizes in different states and different names for the same glass sizes in different states, so it can be a little confusing for visitors. I don't know where the author of this article got the idea that a schooner is two thirds of a pint though, as this size is unknown in Australia.
A schooner in Sydney is three quarters of a pint (originally 15 ounces, but these days rounded to 425ml as Australia uses the metric system). A schooner in South Australia is these days a half pint (10 ounces, 285ml) but used to be smaller (9 ounces, 255ml). However, what is called a pint in South Australia is three quarters of a (British) pint, and the same as a schooner in Sydney. The Sydney schooner size used to be uncommon elsewhere, but has become more available nationally in recent times, although it is still relatively rare in Melbourne and Perth. The half pint is available just about everywhere (and always has been) but under a variety of different names (middy/handle/pot/ten).
The (British) pint is not a traditional glass size in Australia, but has become more common in recent times, possibly due to the opening of theme Irish pubs. This is a bit silly - in hot weather you want to drink from smaller glasses so you are finished before the beer gets warm.
On the other hand, allowing pubs in the UK to serve in whatever glass size they like strikes me as sensible. I sometimes frequent a Portuguese place in Stockwell that serves beer in 0.2 litre and 0.4 litre sizes. They have imported the original Sagres glasses from Portugal to serve it in, and are just being culturally authentic. However, at the moment they are breaking the law. Polish places sometimes sell beer in 0.3 and 0.5 litre glasses, which are the standard sizes in Poland. Once again, why not? Many continental types care more about the beer being served in the original branded glass from the brewery. Forcing them to make glasses in non-standard sizes if they want to sell draught beer in the English market seems silly.