Adding to DrLMG's reply - preference list is needed in case you're so brilliant you qualify for both UWA and Curtin place offers for example.
If these offers are released in the same offer round, TISC only gives you the higher pref one and diverts the other to another applicant. They won't give you both offers which would let the other poor soul hanging.
So the risk of putting UWA > Curtin is if you qualify for both you'd get UWA while your real preference is Curtin.
You are most likely wrong
Except 1 or 2 "weird" schools (fortunately they are not in WA), the pref list is only used by TISC at the offers stage.
Interview invites are issued directly from the schools to applicants. They don't go through the preference process.