Seems like EBay is offering this as a small consolation for the messed up offer https://www.ozbargain.com.au/node/524398. It did show up in my Promotions dashboard when I activated the offer.

You might be able to add it to the original deal if you managed to get EBay to fix that. Yes, I know you can also get 2 free ones via Gumtree as well.