It isn't false advertising unless the listing states "Made in Australia".
Like you, I prefer to buy from Australian sellers, and I would love to see more high-quality manufacturing in Australia. There are companies and shops in Australia that do sell Australian-made products (although it may not be the case for every single item that they sell); we as buyers should check the product details / specifications to see if the country of manufacture is shown. If it isn't, one can always phone the company and ask.
If an eBay seller doesn't have an established Australian business presence, complete with ABN and physical location, it is (for some categories of item) unlikely that the seller is selling Australian-made products, although there are always exceptions.
Don't forget, too, that many high-quality items are actually manufactured in China, but it is done to the company's specifications, using the components specified, the raw materials specified, etc., to Australian standards, subject to quality control.
This is in stark contrast to the made-as-cheaply-as-possible-of-cheapest-inferior-components-without-any-quality-control-and-with-indifference-to-actual-specs unbranded stuff knocked up in Chinese factories for direct sale to Australian suppliers who aren't as particular as they should be, and to Australian buyers whose only criterion appears to be how cheap it is.
I won't beleaguer the point any more than that.
