A quote from the last survivor off the plane says that the aisle in front of them was completely clear as they left. In other words, any delays that might have happened weren't actually enough to harm or kill anyone in and of themselves.
90% of highway traffic jams I drive through end up having no visible cause. That doesn't mean that there was never anything in the road causing a slowdown.
(Unless that survivor meant the aisle was free from other passengers, but that ... seems like an unlikely interpretation.)