> The Oxford comma can prevent ambiguity in complex sentence lists. For example, use the Oxford comma before the last item if you’re using a defining phrase applicable only to that final item.

> A defining phrase is essential to the meaning of the sentence. The following examples show how the Oxford comma can affect meaning, using the defining phrase ‘for stockfeed’.

Seems like it provides a clear cut framework for when to use it?

It's an insane section. My reading is:

- Do not ever use the Oxford comma.

- BTW, in case you don't know what an Oxford comma is, here are all the reasons why the Oxford comma is great.

They do this in other places too.

Your argument rests on the assumption that the serial comma is demonstrably preferable, that it is foolish not to use it in all cases. It is possible that the authors of this advice are better placed to asses whether their audience is comfortable with nuance and context. It is how Australians learn to read and write.

Well, the serial comma is demonstrably preferable, full stop, regardless of your appeal to Australian Authority.

But putting that aside, the issue is not whether the Oxford Comma is preferred: it's what this website is actually instructing bureaucrats to do.