It's similar to how Carlton claim to have been around since 1832 (when in fact they were founded in 1903[1]). The fact is that their subsidiary Cascade has been around since 1832 but were bought out by Carlton much later[2], therefore making the claim that Carlton is the "oldest brewery in Australia".
[2]I can't find a reference to which year they were bought out, but the Wikipedia article above does mention they got bought and they mentioned the year when I took a tour of the Hobart brewery.
[1]https://en.wikipedia.org/wiki/Carlton_%26_United_Breweries
[2]I can't find a reference to which year they were bought out, but the Wikipedia article above does mention they got bought and they mentioned the year when I took a tour of the Hobart brewery.