Relative to the ABN page on Ebay this is quoted:

"Businesses registered for VAT (Value Added Tax),GST (Goods and Services Tax) or other applicable indirect/consumption taxes can use their tax or other country specific identification number to register for tax exempt status on eBay. This allows businesses to pay eBay fees without domestic VAT, GST or similar taxes being applied, where applicable."

I was not aware that simply because you are registered for GST this provides you with tax exempt satus?

Rather, you still pay the GST but are able to claim it back as an input credit when you do your BAS.  (Being registered for BAS means of course you need to charge GST (and pay to the ATO) GST on all of your domestic sales.  Sales to overseas parties are exempt from GST.