Well, you see- you have to define “discover”. It really isn’t just "find for the first time’. It’s “find, report back, and get others to listen & record it”.
I wouldn’t be suprised if the Big Chinese fleet happened to spot parts of Australia. But if so, their records were destroyed and no one did anything about it. Same with scattered traders.
For example- who discovered America? Well, certainly the Vikings got here before Columbus. (And, yes, the peoples that would become the native Americans came over the bering land bridge 1000’s of years before that). And they recorded it. But- few knew they had. So- the Vikings get a footnote, and Columbus gets the prize. Not really fair, but.
Now, it is possible that welsh or portugese fishermen discovered the Grand banks 9and thus America) But- if so, they kept it a secret. I wouldn’t be suprised if an odd Phoenician or even Chinese junk got lost and found America- but never got back. So- no prize for them.
I’d say in the case of the Macassan traders- they get a footnote, along with the Dutch. Neither had any idea that they had found a new continent, and likely the Macassans didn’t really care.
So- that’s a final criteria- you have to care, the discovery has to mean something.