My condolensces to the families. A horrible tragedy.
In Dru's defense, the reporting is very misleading. The Umbwe route is an access route to the mountain that guided parties routinely use to access the Baranco Wall which leads to the easier summit route on the other side of the hill.
It sounds as if the accident actually happened on the Western Breach/Arrow Glacier Route, which ascends straight up the 4th class wall from the top of the Umbwe access route. Its a wall of choss and there are places that the route is very exposed, so I'm not surprised the rock fall has dire consequences. But I'm still suprised there were so many people caught, because most of the porters usually walk around to meet the climbers on their descent.