welcome to the forum.
There isn’t a bug here; the reason your other observations (and the extra ones from other users too) are not showing in the project is because the project admin has set one of the filters/requirements so that only species which have been marked as ‘native’ to Australia are included
in iNat, a species has to be manually marked as native (or endemic or introduced) to a place, it’s not something which is automatically applied. So there are thousands of thousands of species which are indeed native to Australia, but they just haven’t been formally annotated as such within iNat.
The best solution here is to ask one of the project admins to edit the project and remove that filter entirely