There is no filter on eBay to prevent Chinese sellers from listing on eBay Australia, or from appearing in search results when you specify Australia only.

eBay have specified “Australia only” in a different way to the way you or I or most people would specify it. That’s because eBay have bought into the concept of “just in time fulfilment”.

See my post here explaining in detail: https://community.ebay.com.au/t5/Buying/Sellers-lying-as-to-their-location-Why-hasn-t-ebay-done/m-p/...