True, but in this case there was major amounts QF metal in queries.
Qantas appear to be targeting final destinations to which they fly to directly and charge a premium for, not just destinations which have 'major amounts' of QF metal along the way.
SYD-SIN is far more likely to trigger a bonus than SYD(-xSIN)-KUL. Why? Well, it makes sense if comparing what Qantas charges for those routes.
Qantas are
by far the most expensive carrier to SIN. A random search for direct SYD-SIN return in J later this year tells the story - SQ $3.1k, BA $3.3k, QF $4.4k. QF can certainly afford to throw in a 50% SC bonus as an enticement considering the (assumed) higher yield. No one in their right mind should be booking QF there unless they're spending someone else's money, or have a sick case of FF Stockholm Syndrome - but QF would be pricing the route based on what the market will bear so someone must be paying it.
On the other hand, QF aren't able to charge the same premiums on SYD-KUL as they a) don't fly direct and b) partner with an LCC for the SIN-KUL leg which doesn't offer a J cabin. Random search for same period - D7 $2k, QF $2.8k, MH $3k - with D7 & MH flying direct. QF obviously have to bring their price down to have any chance at competing, and still potentially give up a seat on the same SYD-SIN flight they could charge $4.4k for. The yield comes down significantly.
Obviously this is all conjecture, but I think this is what's driving the selection of destinations that trigger bonuses, rather than 'how much' QF metal is in an itinerary.
The aim isn't just to get bums in seats, it's to get bums in seats on routes that QF can (and does) charge a lot for. So in short, if you want to trigger a bonus..
Search for SYD-LHR instead of SYD-(xLHR)-DUB
Search for SYD-LAX instead of SYD-(xLAX)-ABQ (I'm not sure whether DFW is targeted, I don't think we've seen a data point for it yet?)
Search for SYD-SIN instead of SYD-(xSIN)-KUL