The 777 OPT does not do a Balanced Field calculation. It does an optimized or improved climb calculation depending on where it is limited. I don't know if the Kiwis have an EFB or if they use RTOW charts. In any case, it very possibly was not a balanced field calcultion so for anyone to suggest that an abort above V1 is not viable is BS. If this is too confusing for you, good. Go to the spotters forum.
They had an incident, no one was hurt, and the a/c can be used again. Good result!!! That's all we know. Pronouncements by wannabes don't further our understanding.
Tosh!
If they were accel stop field limited then they would be off the end.