So the bit that they chose not to model in finer detail is the bit that they say is the most important to their explanation. That makes less sense than a chocolate firegaurd Mick.
They chose not to model everything in finer detail. It was a global model optimization. Because it was the global collapse model. You know that at the point the collapse started the individual connections in question (lots) had already been marked as failed, so modelling in finer detail would have done nothing at all.