although I would not normally recommend anyone in a heavy "Heavy" to abort after V1 I belive that in this case they were closer to a disaster because they DIDN'T abort. In reality they were way below the "true" V1 and thus they had plenty of runway to stop at.
Well that would depend on several factors, for example a lower weight may give a lower flap setting and higher take-off speeds. Also field length and "optimisation" of speeds for climb performance will affect V1 and not necessarily quite the way you might expect. It depends on stop vs go performance.
However, even assuming the only variable as weight, a lower than required power setting would mean V1 was achieved far further down the runway. Furthermore the higher mass would further reduce the likelihood of stopping in time. In fact V1 is not even relevant as the problem would not manifest itself until VR and I am going to speculate that it would have been far too late to stop.
Note, if you will, that I have had an idle half an hour an half a glass of wine to think this through.
The crew on the day had zero time to think yet still managed to react correctly and recover the situation as well as possible under the circumstances. I hope if it ever happens to me I can do as well.