Evan (or someone else), could you please clarify. Do you mean "if the flight has NO first you get . . ."? I have the same query as a WP travelling internationally on a two class QF flight.
If there is no First, you get Business tags. I believe it's covered somewhere in the rules based on the "highest class" of the International flight.
At least some of the outstations (eg Brisbane domestic) have finally got a collection of F tags to apply to bags where applicable. Doesn't always help speed up things but can assist.