There is availability that is:
1. only available online (the contact centres cannot see this inventory)
This sometimes can be Qantas award flights, but often times we are talking about partner programs. Case in point, a colleague of mine wanted to book SYD to POA (via SCL) on LATAM, one of Qantas' award partners. The website was showing availability for the flight for each segment (i.e. SYD to SCL in J and SCL to POA in Y) but couldn't book the two together. Decided to call QFF, the agent could see SYD to SCL in J but not SCL to POA in Y. They advised them to book it as a multi-city, with all flights departing the same day, which they did. Evidently it did not cost any additional points to tack on the SCL to POA sector (likely because the one-way mileage which just below the threshold for the next one-way mileage tier).
As another example, a colleague of mine had was trying to fly CVG to SYD using points. They could see an economy award on AA down to DFW and a QF award flight back to SYD but again couldn't find the two sectors together when searching as a simple oneway for CVG to SYD. Agent couldn't see the AA flight at all, and they ended up doing the same multi-city booking trick.
2. available to all QF channels (contact centre + online)
Generally speaking that will be QF operated flights, although no doubt someone will chime in with a data point of a QF award flight that appeared online but not on the phone.
3. available to everyone worldwide (eg. partner programs)
And this one requires a lot of asterisks. Partner availability can vary from partner to partner. Whereas I cannot find partner availability on LATAM for some flights I want to take within South America booking with QFF I can find those flights on another partner like Alaska. I don't know if there are data points for QF award flights which appeared on partners but not on QFF, so will leave that to the more learned audience to comment on. Also the price can vary considerably. For instance, a flight between South American countries costs 25,000 QFF points IIRC whereas on Alaska it's just 7,500 points.
4. request via robot for platinum and above
And this one is really a roll of a dice, not even the agent can tell you beforehand if there is availability, they simply have to put in the requests (and yes I mean requests, as they usually try a couple of dates/flights as chances most will come back rejected). Now yes there
are articles discussing how you can increase your odds of the seat being released, but they are really guesses at best. I have seen wide open availability where the bot rejected me, meanwhile I somehow managed to snag an international seat with limited business saver availability. And certainly the operator has no intuition either way. These decisions are well above their pay grade, likely made by people in revenue management who have more of an insight into projected load.
-RooFlyer88