Maybe there are experts in the field who'd know about such things, but I feel there is a possibility that passengers grabbing their belongings is just another manifestation of the "familiar actions after a traumatic event" syndrome. It happens on a lot of occasions - I remember a vivid image after one of the towers collapsed on 9/11 with a guy walking out of the debris, completely caked in dust, yet still carrying his briefcase and newspaper.
Human behaviour in extreme circumstances is unpredictable - examples such as people heading for a more distant emergency exit instead of the closest, or remaining seated despite calls to evacuate, are not unheard of. Perhaps using this accident as a way of investigating the issue would help in future evacuations.