Again, fairly technocratic, but. I know many at the time saw the reigning in of states rights as less about preventing crap like the NT restricting Aboriginal marriages based on caste membership and more about stopping gay people from eventually wanting to call their legal union a 'marriage' as is happening now.
I mean, if the argument is merely a legal one, it just adds fuel to the fire of those who insist it's the definition that needs to change. Before 1965, my Dad was legally not a citizen of this country (despite being born on the Pt Pearce Mission) but registered in the census as livestock. Of course, giving someone like him personhood is a bigger fish to fry (legal rights to own land, vote and whatnot) but you can imagine it wouldn't make gay people looking to have their relationships recognised as equal in every way feel much better to look at it that way considering that one did eventually get changed even before the referendum.