That's certainly true for the US and South American athletes but there are quite a few Euro's on the start list as well. I'm not sure what the travel logistics are like to Australia compared to the US for a Euro athlete.
Texas from Europe is easier....also 7 hour time zone moving west (sleep in before your big race)....vs 6ish time zone going east and a much longer flight...and you are doing the start of the race in the middle of your REM sleep which just sucks if you are trying to do pro level performance. Texas from Europe is a much better "in and out" performance oriented trip. If you go to Aus from Europe, then may as well spend a longer time there to get the body adjusted, but time away from home costs $$$ and $$$ is what pro triathletes don't generally have!