i see sites likes seats.aero and roame.travel showing amex to virgin australia, however i don't understand how this works.

my amex account lets me transfer to virgin atlantic. however it does not seem like one can transfer from there to virgin australia.

trying to get my parents in chicago out to sydney where my sis is having a baby. i find 95% air india and an occasional qatar, although of the few qatar flights available 80% seem only to be from virgin australia and 20% from flying blue.

is amex transfer to virgin australia only for something like australian cardholders? or am i completely missing something here?