Maybe a help. Flew 'direct' 'onestop' BKK-AKL (747 via Syd, TG991), return AKL-BKK 'direct' 'non-stop' (A346 TG990).
Mile posted were exactly the same BKK-AKL and AKL-BKK despite the (small) GC distance difference of about 75miles induced by stopping SYD outbound.