UPDATE:

So I just flew from SYD-DPS on Qantas and had AB Silver (OW Ruby) status. I didn't end up bringing a second bag because I was afraid of the insane 2nd checked bag fee. I did ask the counter agent to clarify the policy for future trips and she said OW Ruby get same baggage benefits of Qantas Silver which is an extra 15kg allowance on top of 30kg standard allowance. Can be as many bags as you want as long as you don't go over 45kg. Really annoying the website doesn't clarify this but hopefully this is helpful for future flyers.