Thanks for that. This does clear things up.
Another question, does ITA Matrix and Expert Flyer mimic a GDS?
Like for example I found a fare with Qantas/SWISS for $1454 (AUD) from Brisbane to Budapest (on skyscanner). But the best I can find on ITA Matrix/Google flights is $1516 (AUD) with Thai/Lufthansa.
Failing this, would I then be able to find the $1454 fare on a GDS such as amadeus?