I wonder if BA is not as knowledgable as AA. I had tentative BA schedule:

... AKL-MEL-PER-SYD-MEL... and BA told me that MEL-PER was considered transcon (as is PER-SYD), and that I am allowed only 1 transcon Australia. However, I had a new RTW with same routing ticketed by AA last week without problem and indeed my current RTW, which I complete next month, has that same routing. Maybe they have different rules?