I think you are confusing the warranty issue in regard to not applying to an individual or overseas seller. If it is an Australian business then a warranty does still apply whether secondhand or a new product. Secondhand items from a business still needs to meet a certain standard and any warranty issues will be delt with by them not the original manufacturer.

Selling an item on ebay will not let a business seller off the hook for any warranty issues after 30 days.

It only takes a few minutes to work out they are a registered business with an ABN so are an Australian Business.