Grabbed a Qantas business seat on the a380 for a couple weeks out today for 85k points. A couple data points that might be relevant to others:

• Phantom availability on a couple of previous attempts to book this, my theory is that it's related to someone else booking the seat before I got to it. I saw space on a few different days before I was actually able to get it to go through. When booking, clear signs that it's phantom availability seem to be if the direct segment (LAX-SYD) didn't show available but SEA-LAX-SYD did, and also I noticed that it was showing PAE-LAX-SYD as available when the seat really existed, but didn't show it when it was phantom availability (even though it still showed SEA-LAX-SYD). It does seem like space tends to open up fairly frequently though, especially as the date gets closer
• Initially the Qantas site wouldn't let me select a seat and said I needed to wait until check-in, but after 3 or 4 hours I tried again and it worked. And it even let me (as Atmos Gold now for 2026) reserve an extra legroom bulkhead seat which was a nice surprise

Previously had Fiji Airways business locked in for the same date and points which I had found a couple months ago (looks like it got released back and is still available btw), but figured that the single long A380 flight would be a little nicer than having to connect in Fiji. Used the "cancel and book a new flight" option on the Change Flight screen which went through with no problem, including thankfully keeping my original flights on the earlier attempts where I hit the phantom availability issues.