It would appear in this case the crew decided that cleaning up in case of the need to shut down one or more engines with deployed reversers was the priority over the stick shake and that demonstrably worked. The aircraft will fly just fine on the threshold of the stick shaker. It won't fly with two engines out and the gear down. Think Concorde.
Makes a lot of sense. It probably wouldn't have taken much of a reduction in pitch attitude for the aircraft to make ground contact and I expect that would have been beyond the end of the paved surface...
They seem to have ended up in a similar situation to the EK flight out of MEL, i.e. passing the end of the runway in an aircraft almost too heavy to fly in its current configuration, only for completely different reasons. At that point, SOPs get put to one side and as our colleagues from the USA would say, the only option left is to "fly the airplane". Well done.