Yeah cause it's always that simple. Hopefully you never crash and have to endure 40 minutes of slow death because of a security door that's now blocking your rescue. Apart from the reasons for this particular crash it does raise a very valid point.
If the air frame is to bend or mis-shape at all I would suspect the sliding windows will not open. This is also is possible for the door frame. I know of a Dash 8 wreck with the old door. The door was pinned closed, emergency overhead hatch pinned closed, pilots cut out of the aluminum.
As for me, if ever I expect to do a crash landing, or an emergency landing where departure from the runway is more than remotely possible, I will certainly unlatch the cockpit door. Fully opening it is not advisable, as tat door can provide lots of protection from unsecured objects in the cabin, but cracking the door is a good way to minimize the risk of the door becoming jammed due to frame bending. The window and hatch exits should remain closed, as again they offer lots of initial protection, and add to the rigidity of the airframe. The cockpit door, however, serves no such purpose. Crack the door!